Colorado’s unofficial severe weather season is during the months of May and June. However, as we look back in Denver weather history, we see that July can oftentimes hold its own. Many occurrences of flooding, scorching heat, and even tornadoes have been recorded. Most notably, this week marks the 24th anniversary of the Big Thompson Flood – Colorado’s deadliest weather disaster ever.
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In 1934…a streak of 15 consecutive days of 90 degrees ranked 5th on the list of hot streaks. The record of 24 consecutive days was established in the summer of 2008.
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In 2008…a streak of 24 consecutive days of 90 degrees shattered the previous record of 18 consecutive days established in 1901 and 1874. Ironically…no new single day record high temperatures were set in the month of July. In August however…a record of 104 degrees was set on the 1st…and another record of 103 degrees was set on the 2nd. In addition…a record low min of 70 degrees was set on August 2nd.
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In 1987…a streak of 16 consecutive days of 90 degrees ranked 4th on the list of hot streaks. The record of 24 consecutive days was established in the summer of 2008.
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In 1965…heavy showers and thunderstorms doused metro Denver with significant rain each day. Rainfall for the six days totaled 5.16 inches at Stapleton International Airport. Massive rainfall occurred on the 20th…21st…and 25th… Flooding streets and basements and causing streams to overflow. The heaviest rainfall…2.05 inches…at Stapleton International Airport occurred on the 25th.
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In 2003…maximum temperature of 100 degrees on the 24th was a record high for the date. Low temperature of 73 degrees on the 25th was a record high minimum for the date.
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In 1875…brief heavy rain and hail lasted only 5 minutes… But the 1/4 inch diameter hail covered the ground to a depth of 1/2 inch and made the streets look like there had been snowfall. There was much crop damage…especially to corn…and some sheep were killed. Precipitation totaled 0.51 inch in the city.
In 1896…a heavy thunderstorm produced sustained northwest winds to 45 mph with gusts to 50 mph and 1.02 inches of rain.
In 1965…a cloudburst dumped 1.99 inches of rain in 30 minutes at Stapleton International Airport. The storm was accompanied by strong winds gusting to 70 mph. The heavy rain flooded numerous streets in east Denver and Aurora. One inch diameter hail accompanied a cloudburst…9 miles southwest of Denver. A funnel cloud was sighted 25 miles northwest of Denver. In Aurora…there were unofficial reports of 2.30 inches of rain in 40 minutes and 3.30 inches of rain in 30 to 40 minutes. Rainfall totaled 2.05 inches at Stapleton International Airport. Rainfall of 2.42 inches for 24 hours on the 24th and 25th was the second greatest on record for July.
In 1977…a tornado touched down briefly in Aurora southeast of Cheery Creek Reservoir. No damage was reported. A funnel cloud was sighted for 4 minutes by national weather service personnel 10 miles north of Stapleton International Airport near Henderson.
In 1991…heavy rain…up to half an inch in 10 minutes…caused flooding in Westminster…Northglenn…and north Denver where a section of railroad track was washed away. At Stapleton International Airport…heavy thunderstorm rain totaled 1.85 inches and briefly reduced the visibility to 1/4 mile. Hail to 1/8 inch in diameter was also measured. A tornado touched down briefly near Fort Lupton. No damage was reported.
In 1998…heavy monsoonal thunderstorm rains caused flooding and flash flooding in eastern and southern sections of metro Denver…including Englewood and Aurora…when about 2 to 3 inches of rain inundated the area. Both I-25 and I-70 were closed for 2 to 3 hours as several low lying areas became impassable due to the high waters. The water was estimated to be 15 feet deep in one flooded underpass along I-25. As a result…the freeway was closed from south of 6th avenue to university blvd. Standing water forced the closure of I-70 at gun club road east of Denver. In Englewood…U.S. Highway 285 was closed…when high water made it impassable. Several cars were reportedly floating down the roadway near Sheridan Blvd. In Aurora…the intersection at Yale Ave. And chambers rd. Was flooded by high water up to 4 feet deep when a spillway on the high line canal was breached. Lightning also knocked out 11 transformers across metro Denver…causing several small fires and scattered power outages. Flood and flash flooding also occurred north of Strasburg when as much as 2.51 inches of rain fell in an hour. The deluge resulted in considerable flooding of local streets and County roads. Torrential rainfall of 2 to 3 inches in less than an hour triggered a flash flood in Virginia Canyon. County Road 279 between Idaho Springs and Central City was closed for two days to clear debris from mudslides. Several cars in Idaho Springs were washed off the road…and numerous basements were flooded in town. Thunderstorm rainfall totaled 2.69 inches at Denver International Airport.
In 2001…lightning struck two homes in Lafayette…damaging the roof and attic of one and shorting out the electrical system in another. Hail to 1 3/4 inch in diameter was measured 7 miles north of Castle Rock with 3/4 inch hail 7 miles north of Sedalia.
In 2005…heavy thunderstorm rain in the vicinity of the overland wildfire burn scar triggered a mudslide in Jamestown. Rocks the size of bowling balls…along with silt and mud slid down the mountain into the town. No one was injured. One parked car was buried by the debris.
In 2006…heavy thunderstorm rainfall caused flash flooding 1 mile north of the town of Westcreek in southwestern Douglas County. Several maintenance roads were washed out by the floodwaters.
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In 1891…a thunderstorm produced sustained northeast winds to 44 mph with gusts to 60 mph and 0.16 inch of rain.
In 1894…a thunderstorm produced sustained southwest winds to 36 mph with gusts to 58 mph…but only 0.04 inch of rain.
In 1910…the high temperature reached 100 degrees in downtown Denver.
In 1959…a Denver man was stunned while standing by a car that was struck by lightning. He was treated for burns and shock at a local hospital. Thunderstorm winds gusted to 55 mph at Stapleton Airport.
In 1983…two heavy thunderstorms hit the northern and western suburbs. The first drenched Northglenn with an inch of rain in 30 minutes. The second storm dumped an inch or more of rain in Idaho Springs and Evergreen. The heaviest rainfall… 2.90 inches in an hour…caused minor street flooding in Golden.
In 1984…heavy early morning thunderstorms drenched the foothills southwest of Denver. Rainfall to 1 1/2 inches in just 30 minutes occurred between Evergreen and Conifer. In nearby Turkey Creek Canyon…1.80 inches of rain was recorded in 35 minutes.
In 1985…a long rope-like white tornado touched down 5 miles east of Erie and stayed on the ground…mainly over an open field…for 18 minutes. However…the twister damaged a few cars on I-25 and injured 3 people from broken glass. The storm flipped over a van…blew out car windows…and ripped a highway sign. It also blew an outbuilding off its foundation. A tornado also touched down briefly 8 miles north of Bennett. No damage was reported from this storm.
In 1988…a 9-year-old girl was slightly injured by lightning in Parker.
In 2003…a severe thunderstorm in and south of Franktown produced hail as large as 1.75 inches in diameter.
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In 1885…heavy cloudbursts on the palmer divide south of Denver caused flooding on Cherry Creek in the city overnight. The high water washed away street and railroad bridges and a few houses. The flood waters completely inundated the rail yards in lower downtown. This was the worst flood on Cherry Creek since May 19-20…1864…but the damage was mitigated by stream improvements and fewer structures near the channel. There was also no simultaneous flood on the South Platte River to slow the flow of water through the city. Rainfall in the city was only 0.08 inch on the 26th.
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In 1897…an apparent dry microburst produced sustained west winds to 48 mph with gusts to 60 mph and a trace of rain.
In 1901…a thunderstorm produced north winds to 38 mph with gusts to 41 mph and rainfall of only 0.01 inch in downtown Denver. This was the only measurable rainfall of the month… Making this the driest July on record.
In 1953…an unconfirmed tornado in south Lakewood touched down briefly and abruptly dissipated. No damage was reported from the twister.
In 1955…the public sighted a funnel cloud estimated at 500 feet above the ground near the western edge of Lowry Field. Wind estimates up to 60 mph were reported in the vicinity.
In 1956…a severe thunderstorm produced 3/4 inch diameter hail and wind gusts to 48 mph at Stapleton Airport where rain fall totaled 1.08 inches.
In 1965…a tornado was sighted 21 miles south of Denver in Douglas County. No damage was reported.
In 1977…a thunderstorm wind gust to 51 mph was recorded at Stapleton International Airport. A funnel cloud was sighted by an aircraft east of Parker.
In 1982…heavy rain doused Boulder with 1 1/2 to 3 inches of rain over a short period of time…causing extensive street flooding.
In 1984…strong thunderstorms drenched several areas. Rainfall of 1.04 inches occurred in just 20 minutes at Boulder. Downpours also hit Aurora and northeast Denver… Delaying flights at Stapleton International Airport for an hour. Up to 3/4 inch of rain fell in central Aurora in 15 minutes.
In 1989…lightning hit a home in Littleton…setting a bed on fire. Damage was confined to the bedroom.
In 1994…lightning struck a furniture store in Boulder… Igniting a fire which caused major damage to the building and contents.
In 1997…lightning sparked a fire…causing extensive damage to a home in Watkins. Heavy rain caused Lena Gulch to surge 2 feet over its banks in Golden. The fire department had to rescue a man when his van stalled in high waters. High waters from swollen creeks and streams washed out bridges and several sections of road in southeast Aurora. A 200-to-300 foot section of road was washed away where Piccadilly Street dips across coal creek. Three youths had to be rescued when they became stranded by rapidly rising water in another normally dry creek bed.
In 1999…lightning was suspected of igniting a fire which caused substantial damage to a farm in Hudson. The blaze destroyed a 10-foot by 60-foot metal pole barn…a pick-up truck…a SUV…a boat and trailer…3 four wheeler vehicles… And other farm equipment.
In 2007…a man was struck and killed by lightning while jogging at Matthews Winters Park in Morrison.
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In 1956…96 percent of the total precipitation for the month of July occurred over the last five days of the month. Heavy thunderstorms produced 4.00 inches of rainfall at Stapleton Airport. This amount of precipitation in 5 days or less had been exceeded only 3 times in previous record. The last time had been in December of 1913 as snow. Considerable property damage occurred across metro Denver from flooding.
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In 1882…intense thunderstorm lightning struck a number of places in the city…but no significant damage was reported.
In 1910…heavy thunderstorm rainfall totaled 2.21 inches in downtown Denver. Rainfall was 1.11 inches in an hour during the early afternoon.
In 1922…heavy rainfall to the south of Denver caused Cherry Creek to rise to the top of the retaining walls in the city. The creek did not flood; however…the large volume of water discharged into the South Platte River did inundate a few blocks of Globeville. Flooding also occurred along Bayou Creek near Franktown to the south of the city.
In 1923…thunderstorm winds were sustained to 38 mph with gusts to 52 mph.
In 1957…iridescent cirrocumulus clouds of unusual formation and brilliant color…oriented from southwest to northeast over metro Denver…were sighted by U.S. Weather Bureau observers at Stapleton Airport shortly after noon.
In 1966…heavy rains from a severe thunderstorm caused flash flooding on deer creek…southwest of Littleton. A child was injured when washed from a car caught in the flood waters. The flooding damaged property along the creek. Strong winds damaged several houses in suburban Littleton.
In 1970…a microburst wind gust to 52 mph was recorded at Stapleton International Airport.
In 1974…a tornado was sighted just east of Buckley Field in Aurora. No damage was reported.
In 1982…up to 2.50 inches of rain drenched an area just southwest of Denver in 30 minutes. This was the second day of heavy rain across portions of metro Denver.
In 1984…1.25 inches of rain fell in 45 minutes in Arvada. Minor flooding occurred on bear creek after a small dam broke.
In 1989…lightning killed two men in Arvada. They were taking wash from a clothesline when a bolt hit the older man…39… Killing him instantly. The bolt then traveled along the line…which was stretched between 2 tall trees…and hit his 26-year-old brother who died the next day.
In 1996…several weak tornadoes developed along a thunderstorm outflow boundary that moved into southern weld…northern Jefferson…and Adams counties. The tornadoes sighted near Bennett…Barr Lake…and in Arvada caused little damage. Strong thunderstorm winds downed several trees in the city of Denver and toppled several trees 7 miles west of Arvada where shingles were blown off several houses. Thunderstorm wind gusts reached 58 mph in Broomfield.
In 1997…a weak tornado touched down briefly in Parker… Damaging a greenhouse. Twenty pieces of the fiberglass roof were ripped away. Heavy rainfall in the foothills washed out some culverts in the pine and conifer areas. Heavy rainfall spread over the plains with 4 to 7 inches reportedly falling near Hudson. Several County roads were washed out between fort lupton and Hudson. Several basements in the area were flooded up to the ceiling. Standing water…up to 3 feet deep…was reported in some backyards. Later in the evening…a flash flood killed 5 people and injured 40 others in two mobile home parks in Fort Collins. The torrential rainfall also caused extensive damage on the Colorado State University campus. Thunderstorm rainfall totaled 0.80 inch at Denver International Airport and 1.09 inches at the site of the former Stapleton International Airport.
In 1999…heavy rainfall…up to 3 inches an hour…triggered a massive rock and mudslide along I-70 near Bakerville. The slide area was about 200 feet wide and 20 feet deep. Several other smaller slides were also reported along the highway. As a result…I-70 was closed for nearly 25 hours in both directions until the debris could be cleared from the roadway. The blockage of I-70 was one of the longest in the history of the highway in Colorado. A severe thunderstorm produced a wind gust to 64 mph at Denver International Airport. The storm also produced 1.56 inches of rain and briefly reduced the visibility to 1/4 mile.
In 2004…a severe thunderstorm produced hail as large as 1 inch in diameter in Thornton.
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In 1889…dense smoke from forest fires in the mountains obscured the sun over the city for three days.
In 1971…a vigorous cold front late on the 28th produced northeast wind gusts to 39 mph and record breaking cold temperatures on the 29th and 30th. The temperature dipped to 47 degrees on the 29th and 43 degrees on the 30th… Setting record minimums for the dates. Upslope cloudiness along with rain and fog early on the 29th helped set a record low maximum temperature of 58 degrees for the date.
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In 1878…a total eclipse of the sun was observed at 2:20 pm. From before to during the eclipse…the temperature in the sun fell from 114 degrees to 82 degrees…while the shade temperature fell from 89 degrees to 83 degrees.
In 1880…heavy thunderstorm rain and hail flooded streets and ditches. In 25 minutes…0.76 inch of rain fell on the city along with large hail to 3/4 inch in diameter. There were no strong winds with the storm.
In 1890…a thunderstorm produced sustained west winds to 48 mph with gusts to 60 mph…but only 0.01 inch of rain.
In 1956…heavy rain and hail fell over west and north Denver.
In 1964…hail to 3/4 inch in diameter fell at Lowry Airfield.
In 1978…a small tornado was sighted just east of Parker. No damage was reported.
In 1989…heavy rain drenched all areas of the Front Range… Both in the foothills and adjacent plains. Amounts of 1 to 3 inches were general over the area. Damage was confined to a few minor road washouts and some street…basement…and crop flooding. Thunderstorm rainfall totaled 1.44 inches at Stapleton International Airport where north winds gusted to 43 mph. Lightning struck a 250 thousand dollar home near Nederland and started a fire which destroyed all of it except two garages. Lightning started a fire in a home in Evergreen. It reached the house by hitting a tree…then traveling through a metal clothesline strung between the tree and the building.
In 1995…thunderstorm winds gusted to 59 mph in Brighton. Thunderstorm winds from the south-southeast gusted to 41 mph at Denver International Airport. High temperature of 99 degrees was a new record maximum for the date in Denver.
In 1997…heavy rain caused flooding in an apartment building in Westminster. Several residents had to be evacuated from their apartments. A woman in Aspen Park received minor injuries…when lightning passed through an office window and struck her. She suffered temporary blindness for about 15 minutes.
In 2003…hail as large as 1 inch in diameter pelted conifer… Highlands Ranch…and Franktown.
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In 1997…heavy rain caused flooding and flash flooding in central portions of Adams and Arapahoe counties. Two homes were extensively damaged when water flooded the basements and adjacent pasture area in Strasburg. Water 4 to 5 feet deep had pooled in the lower lying areas of the town. A portion of Quincy Road was closed in Arapahoe County when 4 feet of water covered the roadway. Rainfall totaled 3.06 inches at Denver International Airport…establishing a new record for 24-hour rainfall in July. The previous record was 2.42 inches set in 1965 on the 24th and 25th.
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In 1879…lightning struck a brick kiln in north Denver. Three men were knocked senseless…but all recovered. Rainfall in the city was only 0.09 inch.
In 1881…a thunderstorm dumped heavy rain and hail on the city…causing street flooding and much damage. A heavy torrent of rain fell with 1.10 inches measured in just 20 minutes. Storm total rainfall was 1.60 inches. The rain turned streets into running streams. Wood street crossings were torn up and washed away. The storm caused great damage by flooding many cellars where goods were stored. The brick yards suffered severe damage when the heavy rainfall destroyed many unfired bricks.
In 1913…northeast winds were sustained to 41 mph with gusts to 48 mph.
In 1939…a thunderstorm produced 0.08 inch of rainfall. This was the only measurable precipitation of the month…making the month the second driest July on record.
In 1961…heavy rain and lightning disrupted power lines and caused flooding in Denver. Thunderstorm rains totaled 1.60 inches at 11th and Lincoln in central Denver.
In 1972…the temperature climbed to a high of 100 degrees at Stapleton International Airport.
In 1983…hail 3/4 to 1 inch in diameter fell in central and southeast Denver and in Littleton. Rainfall of 1.50 inches occurred in just 30 minutes in Littleton. There was some street flooding in both cities with wind gusts up to 55 mph.
In 1984…central Aurora was hit by a downpour that produced 1.80 inches of rain and sent water 2 to 3 feet deep into some streets. Before the rain stopped later in the evening… The storm had dropped as much as 2.80 inches of moisture on the city. Thunderstorm rainfall totaled only 0.82 inch at Stapleton International Airport.
In 1985…a tornado was spotted in open country 10 miles southwest of Bennett. No damage was reported. One inch hail was reported in south Lakewood.
In 1997…one man was killed and his girlfriend critically injured when they were struck by lightning on the Kennedy Golf Course in southeast Denver. Both were struck in the head when they took refuge under a tree during a downpour. Lightning struck a home in unincorporated Arapahoe County east of Buckley Field. The fire started in the electrical panel boxes…causing extensive damage to the home. Heavy rain and hail triggered a flash flood in Boulder…which sent water through a window of the financial aid office on the University of Colorado campus. In addition…ceiling tiles…carpets…and dressing rooms were damaged at the Coors Events Center when a pipe draining rainwater broke during the downpour. In all…10 buildings on the campus received water damage estimated at 100 thousand dollars. Hail as large as 1.25 inches in diameter accompanied the heavy rain in Boulder. Thunderstorm rainfall totaled 2.71 inches at Denver International Airport where west winds gusted to 41 mph. This was the greatest calendar day official precipitation ever recorded in July.
In 1998…heavy rain…up to 3 inches in an hour…caused flash flooding problems from Castle Rock to Parker. I-25 north of Castle Rock was closed as high waters covered sections of the highway. Some cars were left floating in the flood waters.
In 2001…a severe thunderstorm produced a wind gust to 70 mph at a wind sensor on the northeast corner of Denver International Airport.
In 2004…a severe thunderstorm produced wind gusts to 71 mph in Evergreen.
In 2005…the temperature climbed to a high of 101 degrees at Denver International Airport. This was a new record maximum temperature for the date. In addition…this was the 7th day of the month with a high temperature of 100 degrees or more…which set a new Denver record for the most 100 degree days in a month…for a season…and in a year.
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In 1873…the all-time lowest recorded temperature in July… 42 degrees…occurred. The same temperature also occurred on July 4…1903.
In 1874…during the late afternoon rain and hail fell for 5 minutes followed by brief heavy rain. Pieces of solid ice of irregular shape fell upon the roof of the station. The hail stones measured 1 1/2 inches in diameter. Precipitation (rain and melted hail) was only 0.16 inch.
In 1889…the high temperature climbed to 100 degrees in downtown Denver.
In 1919…heavy thunderstorm rainfall totaled 2.59 inches in downtown Denver during the evening. Rainfall was 1.90 inches in an hour…a new record at that time.
In 1961…over an inch of rain in a short period of time caused flooding of streets and basements in Denver. Rainfall totaled 1.30 inches at 11th and Lincoln in central Denver.
In 1964…the temperature reached 91 degrees in Denver…making this the 27th day of the month that the temperature reached 90 degrees or more. This is the all time record for 90 degree days in a month in Denver.
In 1972…one inch diameter hail fell in Hudson northeast of Denver.
In 1976…during the evening hours extremely heavy thunderstorm rains produced flash flooding in Big Thompson Canyon which killed 144 people between Estes Park and Loveland. No significant weather occurred in metro Denver at the time.
In 1987…1 inch diameter hail fell in Lakewood and 3/4 inch hail fell near Louisville. Southeast Boulder County was drenched with 1.25 inches of rain in just 20 minutes.
In 1993…thunderstorm winds damaged a chimney of a home near Parker.
In 1996…a weak tornado (f0) was sighted 12 miles east of Denver International Airport. No damage was reported.
In 1998…heavy monsoonal thunderstorm rain triggered a mud slide in Blackhawk. The mudslide blocked Main St. And caused an estimated half million dollars in damage to a casino. Heavy thunderstorm rain…up to 3 inches in an hour…caused a flash flood along buffalo creek. Portions of County road 126 just south of the town of buffalo creek were washed out. The flood waters nearly washed away the bridge as mud and debris slammed into the structure. Hail to 1 3/4 inches in diameter fell near Idaho Springs.
In 2004…severe thunderstorm winds toppled a 65-foot blue spruce tree in Parker. The tree landed on a home damaging the roof and gutters. The downed tree poked dozens of holes into the shingles.