Category Archives: Climatology

Climatology, Colorado Weather, Thornton Weather

Denver’s 2010 weather – Month by month narrative

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2010 Year in Review - A month by month narrative from the National Weather Service.
2010 Year in Review - A month by month narrative from the National Weather Service.

While Denver’s weather in 2010 was generally pretty quiet that isn’t to say there wasn’t something to talk about.  Below is a month by month narrative from the National Weather Service for each month of the year.

Also be sure to check out Thornton’s 2010 weather year in review.

From the National Weather Service:

JANUARY…ONLY A TOTAL OF 0.07 INCH OF LIQUID EQUIVALENT WAS COLLECTED DURING JANUARY 2010 WHICH CAME FROM MELTED SNOWFALL. THIS IS 0.44 INCH BELOW THE NORMAL OF 0.51 INCH. IT ALSO TIED 1961 AS THE 6TH DRIEST JANUARY SINCE DENVER RECORDS KEEPING BEGAN IN 1872. ONLY 2 DAYS RECORDED MEASURABLE MOISTURE WITH THE 6TH COLLECTING THE MOST IN A 24 HOUR PERIOD WITH ONLY 0.05 INCH. IN THE SNOWFALL DEPARTMENT WHERE MEASUREMENTS ARE TAKEN NEAR THE DENVER INTERNATIONAL AIRPORT (DIA)… ONLY 2.6 INCHES OF THE WHITE STUFF WAS RECORDED. THIS AGAIN WAS BELOW THE JANUARY NORMAL OF 7.7 INCHES. FOR THE SEASON…THE GOOD NEWS IS THAT THE JULY THROUGH JANUARY’S SEASONAL TOTAL WAS 40.2 INCHES WHICH IS 6.9 INCHES ABOVE THE NORM OF 33.3 INCHES FOR THAT PERIOD OF TIME. 40.2 INCHES IS FAR BETTER THAN THE 2008-09 SEASONAL TOTAL THROUGH JANUARY OF A MERE 16.9 INCHES. THERE WERE NO PRECIPITATION RECORDS SET OR TIED DURING THE MONTH.

JANUARY 2010 TEMPERATURE STATISTICS TURNED OUT TO BE A NON-HEADLINE. THE MONTH FINISHED WITH AN AVERAGE TEMPERATURE OF 30.4 DEGREES WHICH IS 1.2 DEGREES ABOVE THE 29.2 NORMAL. TEMPERATURES RANGED FROM A HIGH OF 58 DEGREES DOWN TO A LOW OF A NON-RECORD -16 DEGREES. IN FACT… THERE WERE NO TEMPERATURE RECORDS SET OR TIED DURING JANUARY 2010. ALL 31 DAYS HAD LOW TEMPERATURES AT OR BELOW FREEZING AND 3 DAYS HAD MINIMUM TEMPERATURES BELOW ZERO. TWO DAYS HAD HIGH MERCURY READINGS AT OR BELOW FREEZING. JANUARY 2009 SEEMED LIKE A COOL MONTH AS THERE WERE ONLY 7 READINGS THAT REACHED INTO THE FIFTIES. OBVIOUSLY THE REST OF THE MONTH ONLY SAW READINGS IN THE 40S OR BELOW.

THREE DAYS HAD DENSE FOG (VISIBILITY OF 1/4 MILE OR LESS) RECORDED AT DIA. LIGHT FOG WAS OBSERVED ON 8 DAYS. THE PEAK WIND DURING THE MONTH WAS A FAIRLY LIGHT GUST OF 35 MPH FROM A NORTHWESTERLY DIRECTION (310 DEGREES).

FEBRUARY…IT WAS A COOL FEBRUARY WITH THE MONTH FINISHING WITH A 29.1 DEGREE AVERAGE TEMPERATURE WHICH WAS 4.1 DEGREES BELOW THE NORMAL OF 33.2 DEGREES. EVEN THOUGH IT WAS 4.1 DEGREES BELOW NORMAL…IT WAS STILL 3.9 DEGREES BELOW THE 10TH COLDEST FEBRUARY WHICH WAS 25.2 DEGREES ESTABLISHED IN 1905. THE COLDEST FEBRUARY OCCURRED IN 1954 WITH A VERY FRIGID 17.6 DEGREE AVERAGE. THE FEBRUARY AVERAGE OF 29.1 DEGREES WAS COLDER THAN THE JANUARY 2010 30.4 DEGREE AVERAGE. TEMPERATURES DURING FEBRUARY RANGED FROM A HIGH OF 52 DEGREES ON THE 27TH DOWN TO A LOW OF -1 DEGREE ON THE 9TH. ONLY 3 DAYS DURING THE MONTH REGISTERED HIGHS IN THE 50S. ALL 28 DAYS REGISTERED OVERNIGHT LOW TEMPERATURES AT OR BELOW FREEZING WITH 8 DAYS WHEN THE HIGH TEMPERATURE DID NOT REACH ABOVE 32 DEGREES. ONLY 1 LOW TEMPERATURE DIPPED BELOW ZERO.

PRECIPITATION WAS ALSO BELOW NORMAL. THE MONTH FINISHED WITH ONLY 0.30 INCH OF LIQUID WHICH WAS MEASURED FROM WATER EQUIVALENT OF SNOW. THIS EQUATED TO 0.19 INCH BELOW THE NORMAL OF 0.49 INCH. NINE DAYS RECORDED MEASURABLE MOISTURE BUT THERE WAS NO DAYS THAT ACCUMULATED .10 INCH OR MORE. THE MAXIMUM 24 HOUR LIQUID MEASUREMENT WAS 0.10 INCH BUT THAT COVERED 2 DAYS…THE 7TH AND 8TH. IN THE SNOWFALL DEPARTMENT…5.8 INCHES OF SNOWFALL WAS MEASURED AT THE AIRPORT. THIS WAS ONLY 0.5 INCH BELOW THE NORM OF 6.3 INCHES. THE 24 HOUR SNOWFALL MAXIMUM WAS 1.7 INCHES ON THE 20TH AND 21ST. THERE WERE NO PRECIPITATION OR SNOWFALL RECORDS SET OR TIED DURING THE MONTH. THE DRIEST FEBRUARY WAS 0.01 INCH COLLECTED IN 1970 AND THE WETTEST FEBRUARY WAS 2.01 INCHES IN 1934. THE MOST FEBRUARY SNOW OCCURRED IN 1912 WITH 22.1 INCHES WHILE THE LEAST AMOUNT OF FEBRUARY SNOWFALL WAS A TRACE WHICH OCCURRED JUST LAST YEAR…2009.

THE AVERAGE FEBRUARY WIND SPEED WAS 7.6 MILES PER HOUR WHILE THE PEAK GUST DURING THE MONTH WAS ONLY 35 MPH FROM A SOUTHWESTERLY DIRECTION (210 DEGREES).

Continue reading Denver’s 2010 weather – Month by month narrative →

Climatology, Thornton Weather

Thornton’s December 2010 weather wrap – Month ends drier and warmer than normal again

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Thornton's December 2010 Weather Wrap
Thornton wraps up December with another drier and warmer than normal month.

Much to our dismay we closed out December the same way we did the month prior – warmer and drier than average.  Snowfall continues to elude us this season as we have recorded a mere 4.8 inches thus far which is 20.8 inches below normal.

For the month of December the story was the precipitation, or rather the lack thereof.  A mere 0.22 inch was officially recorded at Denver International Airport and Thornton was only slightly better at 0.28 inch.  This is far below the normal of 0.63 inch for Denver. 

The majority of that precipitation was during the last two days of the month when a very cold and quick snowstorm moved through Colorado.  Were it not for that Denver would have wrapped up the month as the 2nd driest December on record.  Instead the little bit of precipitation that was recorded dropped it out of ‘top 10 driest’ consideration. 

The snow that did fall on the 30th and 31st did not amount to a lot – officially 3.3 inches at DIA.  Thornton was only slightly better with 3.8 inches.  This is again far below the historical average of 8.7 inches for December. 

Continue reading Thornton’s December 2010 weather wrap – Month ends drier and warmer than normal again →

Climatology

Denver’s January weather preview – A look at our coldest month

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Denver's January weather preview.Like any other month in Denver January can yield a wide variety of conditions.  The month is pretty consistently our coldest but by the end of the month we do start to see temperatures slowly start to climb.  Big time snow can and does happen but more often than not the month is quite dry – in fact it is our second driest month of the year.

The real story in January is oftentimes the wind.  Warm but potentially damaging Chinook winds appear with greater frequency and can be a blessing and a curse.  Conversely, cold Bora winds bring dangerous wind chills during the month.

For a complete look at our January weather, a look back at last year and a look ahead at this year’s January weather check out our complete January weather preview.

Climatology, Thornton Weather

Thornton’s November weather recap – Month ends drier and warmer than normal

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November 2010 goes down in the books as drier and warmer than normal. (iStockphoto / johnnyscriv)
November 2010 goes down in the books as drier and warmer than normal. (iStockphoto / johnnyscriv)

November 2010 was most notable not for what weather condition occurred but rather for what it lacked – snow.  Historically November is Denver’s second snowiest month but 2010 saw us receive very little of the white stuff as we start out the season far behind where we average.

At the official Denver weather monitoring station at Denver International Airport a mere 1.5 inches of the white stuff was recorded.  That is 9.2 inches below the historical November average of 10.7 inches.  Despite that, the month fell short of the top 10 least snowiest Novembers as number 10 on that list is 1971 with 1.4 inches.  Given that no snow was recorded in September or October, the 2010 snow season is off to a dismal start at more than 15 inches below normal.

In terms of precipitation, only 0.5 inch was collected in the rain bucket – barely more than half of the normal of 0.98 inch.  While dry, it wasn’t enough to put the month into top 10 driest November status.  Three years in Denver history have recorded only a trace of precipitation and the number 10 slot is held by 1989 when only 0.15 inch of precipitation was recorded.  No precipitation or snowfall records were set or tied during the month.

Here in Thornton we fared drier than the official Denver tallies on all fronts.  We recorded only 1.14 inches of snow and 0.33 inch of precipitation.

Temperature-wise Denver ended the month warmer than normal with an average temperature of 38.3 degrees.  This was 0.8 degrees above the normal of 37.5 degrees.  Temperatures ranged from a high of 77 degrees on the 6th down to a low of 4 degrees on the 25th.  There were 24 days with low temperatures below the freezing mark which is normal.  On only one day, the 29th, did we fail to hit a high temperature of at least freezing as the thermometer only climbed to 31 degrees that day.  No temperature records were set or tied during the month.

Overall Thornton’s average temperature for the month was cooler than Denver’s.  The average temperature was 36.8 degrees with the warmest day hitting 78.7 degrees and the lowest temperature being 9.0 degrees.

Wind is of course a fact of life on the plains and November 2010 did set a new peak wind gust for the month of 55 mph on the 16th.  This easily broke the old record of 49 mph set in 1990.

Click here to view the 2010 Thornton Climate Summary.

CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO
745 AM MST FRI DEC 3 2010

................................... 

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF NOVEMBER 2010... 

CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2010

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH              80   11/08/2006
 LOW              -18   11/29/1877
HIGHEST            77   11/06        79      -2       77  11/05
LOWEST              4   11/25       -18      22       16  11/16
AVG. MAXIMUM     52.6              51.5     1.1     56.4
AVG. MINIMUM     24.0              23.5     0.5     28.8
MEAN             38.3              37.5     0.8     42.6
DAYS MAX >= 90      0               0.0     0.0        0
DAYS MAX = .01         6               5.6     0.4        3
DAYS >= .10         2                MM      MM        3
DAYS >= .50         0                MM      MM        0
DAYS >= 1.00        0                MM      MM        0
GREATEST
 24 HR. TOTAL    0.15 11/16 TO 11/16         0.33 11/14 TO 11/15

SNOWFALL (INCHES)
RECORDS
 TOTAL           42.6  1946
TOTALS            1.5               10.7

DEGREE_DAYS
HEATING TOTAL     793               826     -33      664
 SINCE 7/1       1128              1408    -280     1479
COOLING TOTAL       0                 0       0        0
 SINCE 1/1        870               696     174      533

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
................................................................. 

WIND (MPH)
AVERAGE WIND SPEED              9.7
RESULTANT WIND SPEED/DIRECTION   2/228
HIGHEST WIND SPEED/DIRECTION    45/310    DATE  11/16
HIGHEST GUST SPEED/DIRECTION    55/320    DATE  11/16

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM

NUMBER OF DAYS FAIR            9
NUMBER OF DAYS PC             17
NUMBER OF DAYS CLOUDY          4

AVERAGE RH (PERCENT)     51

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              0     MIXED PRECIP               0
HEAVY RAIN                0     RAIN                       1
LIGHT RAIN                2     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                1     SNOW                       4
LIGHT SNOW                9     SLEET                      0
FOG                      13     FOG W/VIS
Climatology

Globe experiences eighth warmest October on record

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Warm and dry were the key words for Denver’s October weather and that same trend was also seen globally.  According to the National Climatic Data Center, October 2010’s average global temperature was the 8th warmest on record.  With an average temperature of 58 degrees, the month was nearly 1 degree warmer than average. 

The image below shows the areas that were warmer and cooler than the 1971 to 2000 average.

October 2010 global temperatures. (NOAA)
October 2010 global temperatures. (NOAA)

 From the National Oceanic and Atmospheric Administration:

Global Temperature Highlights

  • The combined global land and ocean average surface temperature for October 2010 was the eighth warmest on record at 58.07 F (14.54 C), which is 0.97 F (0.54 C) above the 20th century average of 57.1 F (14.0 C). The range associated with the combined temperature is +/- 0.14 F (0.08 C).*
  • The October worldwide land surface temperature was 1.64 F (0.91 C) above the 20th century average of 48.7 F (9.3 C) — the sixth warmest October on record. Warmer-than-average conditions were particularly felt across western Alaska, Canada, northeastern Africa, the Middle East, Kazakhstan and large portions of Russia. Cooler-than-average regions included most of Europe, Mongolia and much of Australia. The range associated with the land surface temperature is +/- 0.20 F (0.11 C).
    • According to the Bureau of Meteorology, Australia had its 10th coolest maximum temperatures on record for October with daytime maximum temperatures 2.12 F (1.18 C) below average. Statewide, both the Northern Territory and Queensland had their third coolest maximum temperatures since national records began in 1950.
  • The October worldwide ocean surface temperature was 0.72 F (0.40 C) above the 20th century average of 60.6 F (15.9 C) and was the 10th warmest October on record. The warmth was most pronounced across the Atlantic, western North Pacific and most of the Indian Ocean. The range associated with the ocean surface temperature is +/- 0.13 F (0.07 C).
  • For the year-to-date, the global combined land and ocean surface temperature of 58.53 F (14.73 C) was tied with 1998 as the warmest January–October period on record. This value is 1.13 F (0.63 C) above the 20th century average.
  • Moderate La Niña conditions continued in October, while sea surface temperatures remained below-normal across the central and eastern equatorial Pacific Ocean. According to NOAA’s Climate Prediction Center, La Niña is expected to strengthen and last at least into the Northern Hemisphere spring of 2011.

Polar Sea Ice and Precipitation Highlights

  • The average Arctic sea ice extent for October was 2.97 million square miles (7.69 million square km), which was 17.2 percent below average. This marks the third lowest October Arctic sea ice extent since records began in 1979 and the 14th consecutive October with below-average Arctic sea ice extent.
  • Antarctic sea ice began its annual retreat during October. October 2010 was the fourth largest sea ice extent on record (2.9 percent above average). The largest October sea ice extent occurred in 2006.
  •  According to Mexico’s National Weather Service (Servicio Meteorolológico Nacional), this October was Mexico’s driest since 1941.
  • North and west Amazonia in Brazil was in the midst of its worst drought in the past 40 years. In October, one of the Amazon River’s most important tributaries, the Black River, dropped to its lowest level of 44.7 feet (13.6 meters) since record keeping began in 1902.
Climatology, Thornton Weather

Denver’s October 2010 wraps up dry and warm

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October 2010 ended up drier and warmer than normal.
October 2010 ended up drier and warmer than normal.

Following on what was a “top 10” warmest and driest September, October tried to follow suit but fell short of achieving record status.  Nevertheless, the month was considerably warmer and drier than normal. 

In terms of temperature the month ranked as the 11th warmest fall just 0.1 degree short of top 10 status.  The average temperature was 55.3 degrees; a considerable 4.3 degrees above normal.  Temperatures ranged from a high of 85 degrees on the 3rd down to a low of 20 on the 28th.  In all there were only two days when the mercury dipped to freezing or below; seven days below the normal nine we receive. 

Thornton was quite a bit cooler overall than Denver as we had an average temperature of 52.7 degrees.  Highs ranged from 84 degrees on the 4th down to 23.3 degrees on the 28th. 

As an interesting side note, it was just last October that we had our second coldest October on record.  The average temperature in October 2009 was a chilly 42.9 degrees and we had 17 days with temperatures at or below freezing! 

We suffered through another dry month which did spark a couple of wildfires.  A mere 0.54 inch of precipitation was recorded at the official monitoring site at Denver International Airport.  This was just barely more than half of the normal of 0.99 inch.  Most of the precipitation fell in the form of rain on the 12th when 0.34 inch was recorded.  Here in Thornton we were a bit wetter having recorded 0.73 inch of precipitation during the month. 

For the first time since 2003 no snow was recorded in Denver in October.  This is only the 15th time since 1882 that has happened.  On average we expect to receive 4.1 inches of the white stuff. 

See the official statistical summary from the National Weather Service below for more details.  Click here to view the monthly climate summary for Thornton.

CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO
205 PM MDT MON NOV 1 2010

................................... 

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF OCTOBER 2010...

CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2010

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR'S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH              90   10/01/1892
 LOW               -2   10/29/1917
HIGHEST            85   10/03        90      -5       84  10/18
LOWEST             20   10/28        -2      22       17  10/10
AVG. MAXIMUM     69.7              66.0     3.7     54.7
AVG. MINIMUM     40.9              35.9     5.0     31.1
MEAN             55.3              51.0     4.3     42.9
DAYS MAX >= 90      0               0.0     0.0        0
DAYS MAX <= 32      0               0.3    -0.3        3
DAYS MIN <= 32      2               8.6    -6.6       17
DAYS MIN <= 0       0               0.0     0.0        0
PRECIPITATION (INCHES) 
RECORD
  MAXIMUM         4.17   1969  
  MINIMUM            T   1934
TOTALS           0.54              0.99   -0.45     1.36
DAILY AVG.       0.02              0.03   -0.01     0.04
DAYS >= .01         4               5.3    -1.3        8
DAYS >= .10         2                MM      MM        5
DAYS >= .50         0                MM      MM        0
DAYS >= 1.00        0                MM      MM        0
GREATEST
 24 HR. TOTAL    0.34   10/12 TO 10/12     0.39  10/20 TO 10/21       

SNOWFALL (INCHES)
RECORDS
 TOTAL           31.2   1969
TOTALS            0.0               4.1    -4.1       17.2             

DEGREE_DAYS
HEATING TOTAL     300               436    -136      676
 SINCE 7/1        335               582    -247      815
COOLING TOTAL       8                 0       8        0
 SINCE 1/1        870               696     174      533              

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
.................................................................

WIND (MPH)
AVERAGE WIND SPEED              9.1               9.6
RESULTANT WIND SPEED/DIRECTION   3/231            MM
HIGHEST WIND SPEED/DIRECTION    41/350  10/25    37/350  10/29/09
HIGHEST GUST SPEED/DIRECTION    51/350  10/25    54/200  10/05/09

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM                                      

NUMBER OF DAYS FAIR            9
NUMBER OF DAYS PC             22
NUMBER OF DAYS CLOUDY          0

AVERAGE RH (PERCENT)     44

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              4     MIXED PRECIP               0
HEAVY RAIN                0     RAIN                       3
LIGHT RAIN                5     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                       2     FOG W/VIS <= 1/4 MILE      1
HAZE                      7                                           

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.
Climatology

Denver’s November weather preview – Our 2nd snowiest and least sunny month

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Denver's weather in November can bring a wide variety of conditions. What can we expect in 2010? (iStockphoto / johnnyscriv)
Denver's weather in November can bring a wide variety of conditions. What can we expect in 2010? (iStockphoto / johnnyscriv)

Typically November is a quiet weather month with plenty of nice, fall days but it can also turn wet with plenty of snow and moisture.  Just like Forest Gump’s proverbial box of chocolates, you never quite know what you are going to get.

Looking into the weather history books, we see that November is actually Denver’s second snowiest month, second only to March (April is third).  Historically we average 10.7 inches of snow during the month.

One little known fact…  November is the area’s least sunny month, tying with May with only 64 percent sunshine.  September is the sunniest month with sunshine 74 percent of the time. 

Get all the details on Denver’s November weather including a look back through history, a recap of last year and the statistics in our November weather preview.

Climatology

NOAA forecasts warmer than normal winter for Colorado

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NOAA's winter 2010 temperature outlook forecasts warmer than normal temperatures for Colorado.
NOAA's winter 2010 temperature outlook forecasts warmer than normal temperatures for Colorado. (NOAA)

The National Oceanic and Atmospheric Administration released its winter 2010 outlook yesterday and the effects of La Niña are forecast to bring extremes to many places.  Closer to home Colorado’s outlook is for a warm winter with equal chances of above, near or below normal precipitation. 

La Niña conditions have been strengthening in the Pacific which means that water temperatures are cooler than normal.  By contrast, El Niño is the opposite – warmer than normal sea temperatures.  These conditions can have a big effect on weather patterns and can lead to extreme weather events.

“La Niña is in place and will strengthen and persist through the winter months, giving us a better understanding of what to expect between December and February,” said Mike Halpert, deputy director of the Climate Prediction Center – a division of the National Weather Service. “This is a good time for people to review the outlook and begin preparing for what winter may have in store.”

The outlook forecasts a colder and wetter than normal winter for the Pacific Northwest stretching across to the northern Rockies.  Much of the south and southwest is expected to see warmer and drier than normal conditions.

NOAA says Colorado can expect warmer than average conditions in the period through February 2011.  In terms of precipitation, the service does not see any factors that would push us toward one extreme or the other.  As such we have equal chances of above, near or below normal precipitation – essentially a 33 1/3% chance of each.

The precipitation outlook gives Colorado equal chances of above, near and below normal precipitation for the upcoming winter season. (NOAA)
The precipitation outlook gives Colorado equal chances of above, near and below normal precipitation for the upcoming winter season. (NOAA)

Highlights from other regions include:

  • Pacific Northwest:  colder and wetter than average. La Niña often brings lower than average temperatures and increased mountain snow to the Pacific Northwest and western Montana during the winter months, which is good for the replenishment of water resources and winter recreation but can also lead to greater flooding and avalanche concerns;
  • Southwest: warmer and drier than average. This will likely exacerbate drought conditions in these areas. All southern states are at risk of having above normal wildfire conditions starting this winter and lasting into the spring;
  • Northern Plains: colder and wetter than average. Likely to see increased storminess and flooding;
  • Southern Plains, Gulf Coast States & Southeast: warmer and drier than average. This will likely exacerbate drought conditions in these areas. All southern states are at risk of having above normal wildfire conditions starting this winter and lasting into the spring;
  • Florida: drier than average, with an equal chance for above-, near-, or below-normal temperatures. Above normal wildfire conditions;
  • Ohio and Tennessee Valleys: warmer and wetter than average. Likely to see increased storminess and flooding;
  • Northeast and Mid-Atlantic: equal chances for above-, near-, or below-normal temperatures and precipitation. Winter weather for these regions is often driven not by La Niña but by weather patterns over the northern Atlantic Ocean and Arctic. These are often more short-term, and are generally predictable only a week or so in advance. If enough cold air and moisture are in place, areas north of the Ohio Valley and into the Northeast could see above-average snow;
  • Central U.S.: equal chances of above-near-or below normal temperatures and precipitation;
  • Hawaii: drier than normal through November, then wetter than normal December through February. Statewide, the current drought is expected to continue through the winter, with several locations remaining on track to become the driest year on record. Drought recovery is more likely on the smaller islands of Kauai and Molokai, and over the windward slopes of the Big Island and Maui;
  • Alaska: odds favor colder than average temperatures with equal chances of above or below normal precipitation. The interior and southern portions of the state are currently drier than normal. A dry winter may set Alaska up for a greater chance of above normal wildfire conditions in the spring.
Climatology

September 2010 ends as one of the top 10 driest and warmest on record

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The Mile High City's September weather was unusually dry and warm. (iStockphoto / johnnyscriv)
The Mile High City's September weather was unusually dry and warm. (iStockphoto / johnnyscriv)

Wildfires and record-setting temperatures provided a clue as to what the highlights of September’s weather would be and with the month over we now see it in the statistics.  September 2010 will go down in the record books as not only one of the driest Septembers on record but also one of the warmest.

A mere 0.06 inch of precipitation was recorded at the official monitoring station at Denver International Airport over the month.  Most of that fell during a four-day period from the 18th to the 22nd and in the end 25 days had no moisture at all.  That scarcity of precipitation allowed the month to finish in a tie with 1882 and 1920 for the 5th driest September on record.  Here in Thornton we fared a bit better having recorded 0.09 inch of precipitation but that paltry difference is not hardly worth noting.

Not only was precipitation in short supply, so too were even clouds.  Zero days were reported as cloudy, 10 days as partly cloudy and 20 days were fair (sunny).  Thornton recorded over 200 hours of sunshine for the month – more than any other month in 2010.

Temperatures were well above normal for the month and into top 10 status as well.  The average temperature of 67.0 degrees was 4.6 degrees above normal.  This puts September 2010 in a tie with 1939 as the seventh warmest September on record. Thornton was thankfully quite a bit cool as we recorded an average temperature of 64.7 degrees.

Four record high temperatures were tied or broken during the month.  On the 19th a scorching 96 degrees was recorded easily besting the old record for the date of 93 degrees last set in 1980.  That also was the hottest temperature ever recorded that late in the season.  Other dates this past month setting  records were: 94 on the 20th beating the old record of 92 last set in 1956; tied the record on the 26th with 1892;  92 on the 28th topping the old record of 89 last set in 1994.

In all the month recorded eight 90 degree days, well above the normal of 2 for September.  An amazing 25 days had temperature at or above 80 degrees which is the highest number of 80 degree temperatures in September since 1872.  Overall temperatures ranged from the high of 96 on the 19th down to a low of 40 on the 3rd.  Thornton’s temperatures ranged from a high of 93.6 on the 19th to a low of 40.7 degrees on the 7th. 

Looking beyond the statistics, the most noteworthy events of September 2010 were the wildfires in the foothills west of Denver.  The Fourmile Canyon Fire northwest of Boulder became the most destructive in state history in terms of the number of homes destroyed.  West of Loveland the Reservoir Road Fire claimed homes as well but was thankfully controlled relatively quickly due to the quick response of firefighters. 

What does the October 2010 weather hold for Denver and the Colorado Front Range?  Right now the dry and warm weather is expected to continue.  Get all the details in our October 2010 preview. 

From the National Weather Service:

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF SEPTEMBER 2010...

CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2010

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR'S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH              97   09/04/1995
                        09/01/1995
                        09/04/1960
                        09/05/1899
 LOW               17   09/29/1985
HIGHEST            96   09/19        97      -1       91  09/01
LOWEST             40   09/03        17      23       36  09/28
AVG. MAXIMUM     84.8              77.4     7.4     78.0
AVG. MINIMUM     49.1              47.3     1.8     48.9
MEAN             67.0              62.4     4.6     63.5
DAYS MAX >= 90      8               2.2     5.8        1
DAYS MAX <= 32      0               0.2    -0.2        0
DAYS MIN <= 32      0               0.8    -0.8        0
DAYS MIN <= 0       0               0.0     0.0        0
PRECIPITATION (INCHES) 
RECORD  
MAXIMUM         4.67   1961
MINIMUM            T   1892 
                       1944                                           
TOTALS           0.06              1.14   -1.08     0.74               
DAILY AVG.        T                0.04   -0.04     0.02               
DAYS >= .01      3                  6.3    -3.3        5
DAYS >= .10      0                   MM      MM        4
DAYS >= .50      0                   MM      MM        0
DAYS >= 1.00     0                   MM      MM        0
GREATEST
 24 HR. TOTAL    0.03   09/22 TO 09/22    0.42  09/22 TO 09/23       

SNOWFALL (INCHES)
RECORDS
 TOTAL           17.2   1971
TOTALS            0.0               2.1              0.0              

DEGREE_DAYS
HEATING TOTAL      32               136    -104      117
 SINCE 7/1         35               146    -111      139
COOLING TOTAL     100                57      43       78
 SINCE 1/1        862               696     166      533              

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
.................................................................

WIND (MPH)
AVERAGE WIND SPEED              9.3                  9.2
RESULTANT WIND SPEED/DIRECTION   2/190
HIGHEST WIND SPEED/DIRECTION    37/310  09/06    36/210  09/30
HIGHEST GUST SPEED/DIRECTION    44/320  09/06    45/280  09/30

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM                                      

NUMBER OF DAYS FAIR           20
NUMBER OF DAYS PC             10
NUMBER OF DAYS CLOUDY          0

AVERAGE RH (PERCENT)     36

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              3     MIXED PRECIP               0
HEAVY RAIN                0     RAIN                       0
LIGHT RAIN                4     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                       4     FOG W/VIS <= 1/4 MILE      2
HAZE                      2                                           

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.
Climatology, Thornton Weather

The first full month of fall arrives; What will October weather bring to Thornton?

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October is here and it may bring Denver's first taste of snow and freezing temperatures for the season.
October is here and it may bring Denver's first taste of snow and freezing temperatures for the season. (iStockphoto / johnnyscriv)

With the first full month of fall here, October usually brings one of the quietest weather months in the Denver area with plenty of mild, sunny days and clear, cool nights.  Certainly given our recent trend of well-above normal temperatures many are hoping for some relief. 

The month actually has our second highest amount of sunshine with 72 percent with September having the most with 74 percent. Interestingly enough, the month following, November, is one of the lowest sunshine months with only 64 percent.

Typically October brings our first real taste of winter with the first freeze on average coming on the 7th of the month and the first snow on the 15th of the month.

You can get all the details including a look back at historical October weather and a look ahead at what October 2010 is expected to bring in our complete preview here.