Denver’s famously highly-variable weather is very evident in our look back at this week in Denver weather history. Scorching hot temperatures, tornadoes, damaging wind and rain and even significant snowfall all have been seen during this time of year.
From the National Weather Service:
10-17
In 2018…the high temperature equaled or exceeded 90 degrees for 8 consecutive days; breaking the previous streak of 7 consecutive days in the month of September.
10-18
In 2018…the high temperature equaled or exceeded 90 degrees for 9 consecutive days; marking the first time such an occurrence has taken place in the month of September. It also brought September of 2018 into a 4-way tie for most 90 degree + days in the month. Previous years included 2017…2005 and 1895. During the streak…4 record high temperatures were either tied or broken…and one record high minimum temperatures was broken.
11-16
In 2013…a deep southerly flow over Colorado… Ahead of a nearly stationary low pressure system over the great basin… Pumped copious amounts of monsoonal moisture into the area. In addition…a weak stationary front stretched along the Front Range foothills and Palmer Divide. This resulted in a prolonged period of moderate to heavy rain across the Front Range foothills…Palmer Divide…urban corridor. By the 14th…storm totals ranged from 6 to 18 inches… Highest in the foothills of Boulder County. The headwaters then moved down the South Platte River and caused widespread flooding with record flood stages at several locations as it made its way downstream. The record high flood stages resulted in widespread flooding along the South Platte River basin. The flood damage encompassed 4500 square miles of the Front Range…left 7 dead… Forced thousands to evacuate…and destroyed thousands of homes and farms. Record amounts of rainfall generated flash floods that tore up roads and lines of communication… Leaving many stranded. Nearly 19000 homes were damaged… And over 1500 destroyed. Colorado department of transportation estimated at least 30 state highway bridges were destroyed and an additional 20 seriously damaged. Preliminary assessments of the state`s infrastructure showed damage of $40 million to roads and $112 million to bridges. Repair costs for state and county roads ran into the hundreds of millions of dollars. Miles of freight and passenger rail lines were washed out or submerged… Including a section servicing Amtrak`s iconic California Zephyr. The town of Lyons was isolated by the flooding of St. Vrain creek…and several earth dams along the Front Range burst or were over-topped. Floodwaters swept through Estes Park; damaged hundreds of buildings and destroyed large sections of U.S. 34 from Loveland and U.S. 36 from Lyons to Boulder. U.S. 34 suffered the most damage… With 85 percent of its roadway and bridges destroyed. In Weld County…about nearly two thousand gas wells were damaged and had to be closed off as the floodwaters inundated entire communities. Sewage treatment plants and other utilities were knocked out in a number of towns. Governor Hickenlooper declared a disaster emergency on September 13th…in 11 counties across northeast Colorado including: Adams…Arapahoe…Broomfield…Boulder…Denver… Jefferson…Larimer…Logan…Morgan… Washington and Weld. By the 15th…federal emergency declarations covered those counties as well as Clear Creek County. Projected losses from the flooding statewide was nearly two billion dollars in property damage…according to Eqecat… A catastrophe modeling firm. The damage was most severe in and around Lyons and Boulder. More than 11 thousand people were evacuated…reportedly the largest since Hurricane Katrina. President Obama declared a state of emergency for Boulder and Larimer counties. An additional 10 counties were added on the 16th and included: Adams… Arapahoe…Broomfield…Clear Creek…Denver…Jefferson… Morgan…Logan… Washington and Weld counties. The president also declared a major disaster specifically for Boulder County. There were six fatalities directly attributed to flash flooding. Two 19-yr old teenagers died on the 11th…after they were swept away by floodwaters after abandoning their car on Lindon Drive in Boulder. In Jamestown…a 72-yr old man was killed when the building he was in collapsed. An 80-yr old Lyons resident died in the early morning hours of the 12th…when his truck was swept into the St. Vrain River near his home. Later on the 12th…a 79-yr old Larimer County resident was killed when she was swept away while trying to climb to safety from her home in Cedar Point. A 61-yr old cedar point resident died when her home was swept down the Big Thompson River by the floodwaters. An 80-yr old Idaho Springs resident drowned in Clear Creek when the embankment he was standing on collapsed. In Boulder…some of the monthly records broken included: one-day all-time record: 9.08 inches which shattered the previous wettest day of 4.8 inches set on July 31… 1919; one-month record of 18.16 inches…which broke the previous all-time monthly record of 9.59 inches set in May of 1995; wettest September on record which broke the previous record of 5.5 inches set in September of 1940; one-year record of 34.15 inches broke the previous wettest year of 29.93 inches set in 1995. At Denver International Airport…the total precipitation for the month of September was 5.61 inches…which was 4.65 inches above the normal of 0.96 inches. This is the most precipitation ever recorded in Denver for the month of September. Daily precipitation records included 1.11 inches on the 12th and 2.01 inches on the 14th.
15
In 1921…rainfall of 0.02 inch was the only measurable precipitation of the month.
In 1976…the public reported a funnel cloud and golf ball size hail east of Parker.
15-17
In 2000…unusually hot weather for so late in the season occurred when temperatures climbed into the 90’s setting daily record maximum temperatures on each of the 3 days. The high temperature was 92 degrees on the 15th and 95 degrees on both the 16th and 17th.
15-19
In 1906…rain on 5 consecutive days totaled 1.61 inches. A thunderstorm occurred on the 17th. High temperatures ranged from 48 degrees on the 16th to 65 degrees on the 15th. Low temperatures were in the lower to mid-40’s.
16
In 1874…a blast of west winds caused minor injuries during working hours in Boulder.
In Denver…the winds veered suddenly from the southwest to the northwest around noon and increased to a maximum sustained speed of 49 mph behind an apparent cold front. The winds remained strong and backed to the west for the remainder of the afternoon.
In 2000…the record high temperature of 95 degrees at Denver International Airport established or equaled 3 different record extremes: the high temperature broke the previous record high for the day of 92 degrees set over a century ago in 1895; it marked the warmest that it has been so late in September; it also marked the 60th day during the warm season that the temperature had reached 90 degrees or more…equaling the record first set on September 29…1994.
In 2006…strong bora winds behind a pacific cold front raked the eastern slopes of the mountains and metro Denver during the afternoon. Northwest winds were sustained to 40 mph with gusts as high as 54 mph at Denver International Airport.
In 2007…a severe thunderstorm produced a peak wind gust of 67 mph…about one mile east of Bennett. At Denver International Airport…a peak wind gust of 48 mph was observed.
16-19
In 1971…a record breaking early fall snow storm caused extensive damage to trees and utility lines. The heavy wet snow occurred with little wind…but caused record breaking cold temperatures for so early in the season. Snowfall totaled 15.6 inches at Stapleton International Airport with most of the snowfall…12.0 inches…occurring on the 17th. This was the heaviest first snow of the season. The maximum snow depth on the ground was 13 inches. Record low temperatures were set on three consecutive days: 31 degrees on the 17th…23 degrees on the 18th…and 20 degrees on the 19th…which was also a new all-time record minimum for the month at that time. Record low maximum temperatures were set on 4 consecutive days: 48 degrees on the 16th…35 degrees on the 17th…40 degrees on the 18th… And 42 degrees on the 19th.
17
In 1873…brisk west to northwest winds at different times during the day…generally in sudden gusts…spread a good deal of dust into the city.
In 1953…strong winds caused thousands of dollars in damage to Boulder. The winds blew for most of the day with great gustiness…and a freak twister was reported during the afternoon. Damage was minor. A thunderstorm wind gust to 40 mph caused some blowing dust at Stapleton Airport.
In 1992…a tornado touched down briefly near Bennett. No damage was reported.
In 1993…severe thunderstorms rumbled across northern portions of metro Denver. Hail as large as 1 3/4 inches in diameter fell in Brighton. Dime size hail damaged several roofs of residences in Lafayette.
In 2000…for the second day in a row…the high temperature of 95 degrees at Denver International Airport broke three record temperature extremes: the high temperature broke the previous record for the day of 94 degrees set in 1895; it marked the warmest it has been for so late in the season; it also marked the 61st day in the year that the temperature had equaled or exceeded 90 degrees…eclipsing the record equaled the previous day and first set on September 29… 1994.
18
In 1901…northeast winds were sustained to 42 mph with gusts to 50 mph behind an apparent cold front.
In 1948…the low temperature cooled to only 69 degrees…the all-time record high minimum for the month.
In 1988…a strong cold front blasted metro Denver with high winds. Gusts reached 82 mph in Longmont and 81 mph at Jefferson County Airport near Broomfield where the winds flipped over and destroyed a small airplane. Wind gusts to 60 mph were recorded in Boulder and Wheat Ridge. West wind gusts to 54 mph were clocked at Stapleton International Airport. The strong winds downed trees and power lines and damaged homes and cars. A Longmont man was slightly injured…when a tree fell on top of his car.
In 1990…a slow moving thunderstorm over southwest metro Denver spawned an ominous looking funnel cloud near the intersection of Sheridan Blvd. and U.S. Highway 285. The funnel cloud nearly touched down a few times before lifting back into the main cloud. No damage was reported. Pea to marble size hail and 3/4 inch of rain fell over central and northeast Denver. Numerous streets and underpasses became flooded on Denver’s south side when the heavy runoff backed up storm sewers. Thunderstorm rainfall totaled 1.02 inches at Stapleton International Airport.
In 1993…a severe thunderstorm rolled through southeast metro Denver. Dime size hail was reported in many areas. Straight-line winds from the thunderstorm…measured by a weather spotter at 70 mph…tore the roof off 6 apartments of an apartment complex in Aurora. Heavy rain which accompanied the winds caused major damage to the apartments as well as the contents. Many trees…fences… And power poles were knocked down by the strong winds. Heavy rain flooded roadways in Denver and Aurora. Thunderstorm rainfall totaled 1.08 inches and north winds gusted to 44 mph at Stapleton International Airport where the visibility was briefly reduced to as low as 1/4 mile in heavy rain.
In 1996…a late summer snowstorm struck the northern mountains and Front Range eastern foothills. Golden Gate Canyon received 6 inches of new snow with 5 inches reported at both Nederland and Blackhawk. Thunderstorms produced heavy rain across metro Denver…which was mixed with snow by late evening. Rainfall totaled 0.83 inch at the site of the former Stapleton International Airport and 1.22 inches at Denver International Airport where northwest winds gusted to 39 mph.
18-19
In 1955…heavy rains caused flash flooding across portions of metro Denver. Rainfall totaled 1.71 inches at Stapleton Airport.
19
In 1955…hail stones to 2 1/2 inches in diameter were reported north of Denver. The large stones broke many automobile windshields.
In 1963…hail to 3/4 inch in diameter fell in Westminster.
In 1983…an unusually strong cold front roared through metro Denver during the afternoon hours. At Stapleton International Airport…the temperature dropped 51 degrees… From a sunny 86 degrees to a snowy 35 degrees…in just 7 hours. Strong winds and a wall of blowing dust followed the front. Northeast winds gusting to 36 mph briefly reduced the surface visibility to 1 mile in blowing dust at Stapleton International Airport where only a trace of snow fell later.
In 1996…high winds gusting to 84 mph were measured at Golden Gate Canyon in the foothills west of Denver. West winds gusted to only 25 mph at Denver International Airport.
20
In 1921…an apparent bora produced northwest winds sustained to 44 mph with gusts to 64 mph.
In 1955…hail stones 1/2 to 3/4 inch in diameter were reported across parts of the city of Denver.
In 1992…weather observers at Buckley Air National Guard Base sighted two tornados southeast of the base. The tornados were short-lived and caused no injuries or damage.
20-21
In 1963…heavy rain and hail caused local flooding in southeast Denver. Thunderstorm rainfall was only 0.60 inch at Stapleton Airport on the 20th.
In 1983…the cold front on the 19th brought an unusually cold air mass into metro Denver for so early in the season. The temperature dipped to a daily record minimum of 28 degrees on both days.
In 1995…a vigorous late summer storm brought the season’s first heavy snow to portions of metro Denver. Millions of trees were damaged and power lines downed as 4 to 8 inches of heavy wet snow settled on fully leafed trees in the Boulder and Denver areas. Branches snapped and trees split under the weight of heavy snow…downing power lines. Firefighters responded to numerous transformer fires. Around 100 thousand people were left without electricity in Boulder and Denver areas alone. It took over a week to fully restore power to some areas. Insurance claims were estimated to be around 6 million dollars to homes in metro Denver and about 500 thousand dollars in damage to automobiles. It was estimated that about 80 percent of 125 million dollars’ worth of city owned trees in Denver were damaged. Snowfall totaled 7.4 inches at the site of the former Stapleton International Airport where the greatest depth of snow on the ground was only 4 inches due to melting. Temperature records were set on the 21st when the thermometer dipped to a record low reading of 27 degrees and climbed to a high of only 36 degrees… Setting a record low maximum for the date. North winds gusted to 29 mph at Denver International Airport on the 20th.
20-22
In 1902…a thunderstorm on the 20th…in advance of an apparent cold front…produced rain…hail…and northwest winds to 40 mph with gusts to 48 mph. Widespread rain developed behind the cold front and totaled 3.21 inches from the evening of the 20th through the early afternoon of the 22nd. The 2.70 inches of precipitation recorded from 800 pm on the 20th to 800 pm on the 21st is the greatest 24 hour precipitation ever recorded in the month of September. The temperature dipped from a high of 80 degrees on the 20th to a high of only 51 degrees on the 21st.
21
In 1951…4.2 inches of snow fell at Stapleton Airport… Where northeast winds gusted to 27 mph. This was the first snowfall of the season in Denver…marking the end of the second shortest snow-free period on record…109 days…from June 4th through September 20th. A trace of snow fell on June 3rd.
In 1984…thunderstorm winds gusted to 56 mph at Stapleton Airport.
In 1992…the only precipitation of the month at Stapleton International Airport…0.01 inch of rain…fell from a brief shower around daybreak.
In 2009…an early season storm brought moderate to heavy snow to the foothills of clear creek…Jefferson and park counties…west and southwest of Denver. A trained spotter…4 miles west-northwest of Conifer…was the big winner with 14 inches of snow. Storm totals elsewhere generally ranged from 5 to 10 inches.
21-22
In 1870…strong winds occurred in the foothills and in Boulder and Denver.
In 1895…rain changed to snow overnight and totaled 11.4 inches in downtown Denver. This was the first snowfall of the season and the second heaviest first snowfall of the season on record. North winds were sustained to 27 mph with gusts to 30 mph on the 21st.