Category Archives: Climatology

Climatology, Thornton Weather

A preview of Denver & Thornton’s February weather

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February comes and serves as a bit of a month of transition between winter and spring. Average temperatures start to climb and things are generally pretty quiet.

However, it is still winter and below freezing temperatures at night still remain the norm. February is not typically a snowy month – in fact only the 6th snowiest – with an average of 6.3 inches. In terms of severe weather, the month joins September and October as being the quietest for Denver.

As we say though, it is a month of transition and as such extremes can and have occurred in the past. From severe cold and snow to beautiful spring-like days we can see it all. Oftentimes the month can lull us into a false sense of spring when the snowiest month – March – has yet to come.

Get all the details complete with historical extremes, statistics, and more in our complete preview here.

Climatology, National Weather, Natural Disasters

Deadly cold envelops Northern Hemisphere from U.S. to China

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Severe cold weather has enveloped the northern half of the globe from the United States to Britain to China. Across the continents, many places are reporting record setting temperatures and lives have been lost due to the Arctic chill.

The eastern half of the United States saw cold, Arctic air pulled down from the north plunging temperatures below freezing in normally mild places as far south as Florida. The widespread cold gripped most of the nation east of the Rocky Mountains to the Gulf of Mexico and the Atlantic Seaboard.

Across the Midwest, temperatures plunged to well below freezing as parts of Iowa recorded temperatures as low as -15 degrees. Jeff Johnson, National Weather Service meteorologist, told the Des Moines Register, “”We’re a solid 30 degrees below normal.” Minneapolis, Minnesota and Chicago, Illinois were seeing wind chills below 0 degrees Tuesday morning.

In Miami, residents accustomed to short sleeve shirts and shorts bundled up as temperatures dropped to freezing. Further north in the state, Orlando saw a low temperature of 21 degrees.

The National Weather Service issued hard freeze warnings across parts of Mississippi, Alabama, Georgia and Florida as the cold threatened the agriculture industry in those states. Freeze watches in Tennessee highlighted the severe cold and came on the heels of reports that four people have died in that state from the cold.

There's more to this story on Examiner.com!The United States is not alone as the cold has turned deadly across the globe.  Get all the details and see some amazing photos at the Natural Disasters Examiner.

Climatology, Thornton Weather

December 2009 goes into the books as seventh coldest on record

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For the second time in the past three months, Denver has experienced monthly average temperatures in the ‘top 10 coldest’ category. In October, the Mile High City saw its second coldest October on record since record keeping began in 1882. Now Denver has just wrapped up its seventh coldest December in history.

Denver’s average December 2009 temperature was 24.1 degrees – a chilly 6.2 degrees below the normal average of 30.3 degrees. That puts the month into the books as the seventh coldest December on record (image right).  Thornton was just a touch colder having recorded an average temperature of 23.8 degrees.

Temperatures during the month ranged from a high temperature of 59 degrees on the 1st down to a low of -17 on the 9th. Overall, the majority of days during the month saw below normal temperatures.

In terms of snowfall, the month did finish above average but not in record setting territory. The National Weather Service recorded 11.1 inches of snowfall at the official monitoring station at Denver International Airport. This was 2.4 inches above the average of 8.7 inches for December.  In Thornton, we received a bit more snow than DIA.  15.3 inches was recorded at ThorntonWeather.com of which the single biggest even was the pre-Christmas storm which dumped 7.5 inches.

 The snow we did receive however was rather dry and as such we finished the month below normal for precipitation. DIA recorded 0.45 inch of precipitation which is 0.18 inch below normal.  Here again, because of the additional snowfall, Thornton fared a bit better with 0.5 inch of precipitation. 

CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO                                 
510 PM MST SAT JAN 2 2010

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

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF DECEMBER 2009...

CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2009

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR'S         
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)      
                                          NORMAL                      
................................................................
TEMPERATURE (F)
RECORD
 HIGH              79   12/05/1939                                    
 LOW              -25   12/22/1990                                    
                        12/24/1876                                    
HIGHEST            59   12/21        79     -20       69  12/02       
                        12/01                                         
LOWEST            -17   12/09       -25       8      -19  12/15       
AVG. MAXIMUM     36.4              44.1    -7.7     41.0              
AVG. MINIMUM     11.9              16.4    -4.5     12.3              
MEAN             24.1              30.3    -6.2     26.6              
DAYS MAX >= 90      0               0.0     0.0        0              
DAYS MAX <= 32     15               5.3     9.7       10              
DAYS MIN <= 32     31              29.2     1.8       30              
DAYS MIN <= 0       6               2.8     3.2        6              

PRECIPITATION (INCHES)
RECORD
 MAXIMUM         5.21   1913                                          
 MINIMUM         0.00   1881                                          
TOTALS           0.45              0.63   -0.18     0.24              
DAILY AVG.       0.01              0.02   -0.01     0.01              
DAYS >= .01         7               5.3     1.7        6              
DAYS >= .10         2                MM      MM        0              
DAYS >= .50         0                MM      MM        0              
DAYS >= 1.00        0                MM      MM        0              
GREATEST
 24 HR. TOTAL    0.20   12/22 TO 12/23        0.10  12/13 TO 12/14       

SNOWFALL (INCHES)
RECORDS
 TOTAL           57.4   1913  SNOWIEST DENVER MONTH SINCE 1881
TOTALS           11.1                8.7              7.1             

DEGREE_DAYS
HEATING TOTAL    1260              1078     182     1179              
 SINCE 7/1       2739              2486     253     2367              
COOLING TOTAL       0                 0       0        0              
 SINCE 1/1        533               696    -163      825              

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

WIND (MPH)
AVERAGE WIND SPEED              8.8
RESULTANT WIND SPEED/DIRECTION   3/217
HIGHEST WIND SPEED/DIRECTION    43/220    DATE  12/13
HIGHEST GUST SPEED/DIRECTION    49/220    DATE  12/13

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM *SUNSHINE DATA N/A EFFECTIVE 10/1

NUMBER OF DAYS FAIR            4
NUMBER OF DAYS PC             21
NUMBER OF DAYS CLOUDY          6

AVERAGE RH (PERCENT)     61

WEATHER CONDITIONS. NUMBER OF DAYS WITH 
THUNDERSTORM              0     MIXED PRECIP               0
HEAVY RAIN                0     RAIN                       0
LIGHT RAIN                0     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       2
LIGHT SNOW               10     SLEET                      0
FOG                      11     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, Thornton Weather

Denver gets new National Weather Service weather station near downtown

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Denver now as an official weather monitoring station closer to downtown but some say this doesnt solve the problem of the citys climate records being altered. (Examiner.com)
Denver now as an official weather monitoring station closer to downtown but some say this doesn't solve the problem of the city's climate records being altered. (Examiner.com)

It only took 14 years but Denver finally has an official monitoring station near downtown again. The new station amongst the greens of City Park Golf Course finally gives residents of Denver a place to see what the weather is doing closer to home.

With the opening of Denver International Airport in 1995, the National Weather Service moved its station to the new airport. That distance of 12 miles from the old Stapleton facility to DIA confounded citizens, television meteorologists and weather enthusiasts as they all noted that no one lives out at the airport and the conditions reported there do not reflect what is happening closer to town.

Recognizing the problem, a public-private partnership came together to do what they could to rectify the problem. The City and County of Denver, the Denver Museum of Nature and Science, the National Weather Service and NOAA, 7News Chief Meteorologist Mike Nelson and Colorado State Climatologist Nolan Doesken identified a site for the new station.

Eclar Fence and Mercury Electric donated the infrastructure for the new site. Weather equipment manufacturer Vaisala donated the weather monitoring hardware and services, estimated at up to $60,000.

Certainly there is little doubt the new station will provide area residents the ability to view conditions closer to where they actually live. The new station will not however address the very real problem of Denver’s climate records having been altered since the move to DIA. The National Weather Service has said the official records for Denver will still come out of DIA and as such many believe those records come with an asterisk.

There's more to this story on the Denver Weather Examiner's site!Why is there still a problem with Denver’s climate records?  What does the new station look like?  Check out the complete story including photos of the station, an interactive map and more on Examiner.com.

Climatology

October 2009 ends as second coldest and fifth snowiest on record

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October 2009 in Denver was the second coldest and fifth snowiest October on record.
October 2009 in Denver was the second coldest and fifth snowiest October on record.

Most of the month of October was cooler than normal in the Mile High City and now that the month is over we see just how cold it was. Denver finished October 2009 with an average temperature more than 8 degrees below normal and had 9 inches more snow than what is normal for the month.

October 2009’s 42.9 degree average makes it the second coldest since record keeping began in 1873 – 136 years ago! re in Thornton we were actually slightly cooler with an average temperature of 42.0 degrees.  Only October 1969 was colder as that year Denver had an average temperature of a chilly 39 degrees.  He

Across the board temperatures for the month were well below normal. The average daily high temperature of 54.7 degrees was 11.3 degrees below the normal of 66.0 degrees. Low temperatures were similarly well below normal with an average of 31.1 degrees – 4.8 degrees below the normal of 35.9. 

Thornton was warmer for daytime highs than the Denver official temperatures as we averaged 55.6 degrees.  In terms of low temperatures, we were cooler having averaged 30.7 degrees. 

There's more to this story on the Denver Weather Examiner's site!What about the snowfall?  Denver finished with the fifth snowiest October on record.  Click here to get all the details on Examiner.com.

Why do we link to Examiner.com?  Click here to find out.

Climatology, Thornton Weather

Thornton’s November weather preview – Our second snowiest month

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November is Denvers second snowiest month. What else can we expect?
November is Denver's second snowiest month. What else can we expect?

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.

In 1994, November was the snowiest month of that year with 16.9 inches – over 12 inches of which fell within a 12 hour period on the 13th and 14th.  In 1991 we saw 29.6 inches of snow (the 2nd snowiest November) and the following year in 1992 we had 20.1 inches of snow (the 8th snowiest November).  Those examples though pale in comparison to the snowiest November on record which was in 1946 when a whopping 42.6 inches of snow fell! 

It isn’t always that snowy though. November 2002 was at the time the 16th month in a row with below normal precipitation and the calendar year of 2002 marked the driest in Denver weather history. This pattern of below normal precipitation continued for 19 months through February 2003. Since 1882, one year (1949) recorded no snow, six more recorded only a trace of snow and four had less than one inch of snow.

For the rest of the November weather preview including complete historical statistics, averages and much more, click here.

Climatology, Thornton Weather

Preview of Thornton’s October Weather – Fall is Here

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What does October weather hold for Denver?
What does October weather hold for Denver?

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. 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.

Average temperatures in October steadily drop throughout the month. On the first we average 72 degree highs but by the 31st that drops to 59 degrees. October also sees our average low temperatures start to reach below freezing as well. At the start of the month we will average 42 degrees as the low temperature but by the end of the month the mercury dips to 30 degrees. This truly begins the sign that winter is approaching.

Get all the details on Denver’s October weather in our complete preview here.

Climatology, National Weather

NOAA: Summer 2009 was 34th coolest on record; thousands of low temp records set

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Highlighting the cooler summer, thousands of record low temperatures were experienced in July 2009. (NCDC)
Highlighting the cooler summer, thousands of record low temperatures were experienced in July 2009. (NCDC)

The National Oceanic and Atmospheric Administration (NOAA) announced this week that the summer of 2009 was the 34th coolest since 1895. Covering the months from June to August for the contiguous United States, the average temperature was 0.4 degrees below the 20th century average.

Emphasizing the lower temperatures experienced in the United States over the summer, a closer look at the statistics provides some telling information.

Over the three month period, stations reporting to the National Climatic Data Center (NCDC) showed 2,254 daily record low temperatures and 1,296 low temperature records were tied according to preliminary data. Similarly, 4,051 daily record low maximums were recorded and 1,501 records were tied across the nation during the summer.

July in particular was notably cooler than normal and the single month by itself counted for roughly half of the records set across the three month summer. For the month, 2,212 record low maximum temperatures were recorded and 737 were tied. 1,225 new record low temperatures were recorded and 657 records were tied.

There's more to this story on the Denver Weather Examiner's site!For all the details on the United States’ summer weather including NOAA’s summary and a look back at the country’s August weather, go to Examiner.com.

Climatology, Thornton Weather

August 2009 climate and weather preview posted

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Thorntons August weather preview.
Thornton's August weather preview.

As summer vacations wind down and families prepare to send their kids back to school in August, Colorado weather also starts to settle down. The chances for severe weather decrease markedly during August and by the end of the month daytime temperatures are dropping quite a bit as well.

At the start of the month Denver usually averages around 88 degrees for a high temperature. By the end of August that drops to 82 degrees. Similarly, nighttime lows drop from 60 to 53 from the start to the end of the month. Generally clear skies can be expected between midnight and noon but the afternoon often brings showers and thunderstorms. These storms typically develop over the foothills then bring precipitation to the Denver metro area.

Despite that moisture, the chance for severe weather decreases considerably compared to the first two months of summer. Cooler air near the surface helps to create a stable atmosphere thus keeping thunderstorms from usually becoming too intense. After the middle of August, tornadoes and damaging hail are pretty rare. The slow movement of storms this time of year are more likely to produce potentially heavy rain.

Click here to read the complete preview including a look back at what was a record setting month last year.

Climatology, Colorado Weather, Thornton Weather

July 12 to July 18 – This week in Denver weather history

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July 12 to July 18 - This week in Denver weather history
July 12 to July 18 - This week in Denver weather history

A busy week in Denver weather history for sure.  Most notable are the occurences of flooding that seem to happen with regularity as well as the costliest hail storm in American history.

11-12

In 1872…heavy rain from 4:00 pm until 2:00 am caused much damage.  Rainfall totaled 1.76 inches.

12   

In 1881…during the early evening…a brisk rain fell for 30 minutes from a nearly clear sky containing not one tenth of clouds with the sun shining brightly.  Rainfall was 0.16 inch.
 
In 1885…thunderstorms produced widespread lightning across the city during the evening.  Several people were injured when their homes were struck by lightning.
 
In 1954…the high temperature reached 101 degrees at Stapleton Airport.
 
In 1962…lightning struck and killed a Denver man…while he was assisting a co-worker with his car.
 
In 1971…the temperature climbed to a high of 101 degrees at Stapleton International Airport.
 
In 1974…hail to 3/4 inch in diameter fell in Castle Rock.
 
In 1991…hail to 2 inches in diameter fell in Thornton with golf ball size hail in Brighton.  Dime size hail was recorded in the city of Denver.  Very heavy rain caused flooding across metro Denver.  Water was up to 2 feet deep in parts of Golden where one foot of water was reported in the lot of a mobile home park.  Flood water washed away part of a parking lot at the Colorado school of mines in Golden. Heavy rain caused a rock slide and flooding along I-70 in the foothills just west of Denver.  Flood waters were a foot deep at the intersection of I-70 and I-25 just north of downtown Denver.  A funnel cloud was sighted just east of the rocky mountain arsenal.
 
In 1996…very heavy rainfall from a fast moving thunderstorm dumped 2 to 3 inches of rain within an hour over southern Jefferson County.  Two people were killed near the town of buffalo creek when a 20-foot wall of water flooded the area.  Utility poles and trees were uprooted; cars… Propane tanks…and bridges were destroyed in the flood’s path.  Entire buildings were moved from their foundations and heavily damaged by the floodwaters.  The first fatality occurred along State Highway 126 when the driver of a pick-up truck was washed off the road by the deadly wall of water.  The second death occurred farther upstream when a man in a 5th-wheel trailer was washed away.  This was the second disaster to strike the area in the last couple of months.  The community was already recovering from a wildfire which burned about 12 thousand acres of forest land in late May.  With the forest burned by fire…very little vegetation was available to slow the storm’s runoff…which resulted in the flash flood.  Power…water…and sewer service were heavily damaged in the flood and…in some cases…beyond repair.  The cost of repairing the roads and water system in the area was estimated at around a half million dollars.  Elsewhere across metro Denver…severe thunderstorms produced hail…damaging winds…and small tornadoes.  Weak tornadoes (f0) were reported in Broomfield… 3 miles east of Englewood…and in Dacono.  No damage was reported…except a trampoline was blown into a window and several trees were downed in Broomfield.  Thunderstorm wind gusts estimated as high as 60 mph blew a fence down in Louisville where winds also toppled a tree near a house. The house received only minor damage.  Large hail…strong winds and heavy rain caused substantial property damage in portions of southeastern Boulder and northern Jefferson counties.  Damage estimates in the Broomfield area alone were about 1 million dollars.  Winds gusted to 81 mph in Broomfield.  Large hail…3/4 to 1 1/2 inches in diameter fell in Evergreen…Lakewood…Englewood…Broomfield…near Morrison…northeast of Boulder…and just east of Denver International Airport.
 
In 2000…heavy rain fell across a portion of the hi meadow fire burn area near buffalo creek…causing localized flooding.  About 3/4 inch of rain fell in 30 minutes over miller gulch.  Some culverts become plugged by debris from the fire.  As a result…small sections of a u.s. forest service road along miller creek were washed out.  Lightning struck a home in Castle Rock…causing extensive damage to the roof…attic…and second floor.

Continue reading July 12 to July 18 – This week in Denver weather history →