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Denver Climatological Preview - August 2009 |
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Preview of Thornton's August Weather - The Winding Down of Summer
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. As the end of the month comes, we start to notice our daylight hours getting fewer and even a bit of a nip in the early morning air. Historical temperature extremes for August are somewhat interesting. First, the highest temperature ever reached in Denver was actually recorded in August - 105 degrees on August 8, 1878 (also tied on July 20, 2005). Second, while there has never been snow in Denver in August, twice the mercury has dropped to 40 degrees to serve as a reminder the white stuff isn't too far off - those occurrences were on August 22, 1904 and August 24, 1910. Looking back at August 2008 - A record setting month August 2008 was notable in Denver weather history for many reasons including a record setting heat wave and being a very wet month. Denver started a record 24 consecutive day 90 degree streak on July 13, 2008 and it ended on August 5th. That smashed the old record of 18 days set in 1874 and 1901. August 1st also hit a high temperature of 104 degrees breaking the old record for that date of 100 degrees last set in 1938. The heat continued on August 2nd with a high temperature of 103 degrees, breaking a 130 year old record of 100 degrees set in 1878. That same day, the low temperature of 70 degrees set a record low minimum for the date, breaking the record of 68 set in 1878. Mercifully, Thornton wasnt quite as warm as it was out at DIA where Denvers official measurements are taken. We recorded a high temperature of 100.6 degrees on the 1st and our streak of 90 plus degree days numbered only 18. It wasnt however entirely hot during the month as two record low maximum temperatures were also set. On the 15th the mercury only reached 59 degrees, breaking the old record of 63 set in 1890. The was followed by a high temperature of 58 degrees on the 16th, five degrees below the previous record of 63 set in 1890 as well. Thornton was just a touch cooler on those record setting days having recorded a high temperature of 58 on the 15th and 57.2 on the 16th. Similarly, low temperatures on those days dipped a bit lower to 49 on the 15th and 49.6 on the 16th. Overall, temperatures ranged from a high of 104 of the 1st of the month down to 50 degrees on the 15th and 16th (100.6 and 49 in Thornton). The average temperature of 71.6 was 0.1 degree below the normal for August. Ten 90 degree days were recorded which is only one above normal. In terms of precipitation, with 4.03 inches recorded, August 2008 became the third wettest on record. This measurement was well above the normal of 2.21 inches for the month. On the 6th, 1.29 inches of rainfall was recorded at Denver International Airport, breaking the previous 24 hour precipitation record of 1.10 inches set in 1929. The day prior, the 5th recorded 0.70 inch, a mere 0.01 inch away from breaking a record also. The month was the first month since October 2007 to have above normal precipitation in part thanks to four days with over ½ inch of precipitation and two with more than 1 inch. In all, twelve thunderstorms were recorded at DIA but none reached the severe level. This was four more than the normal of eight days with thunderstorms Denver receives on average in August. Outlook for August 2009 The National Weather Service 30-day outlook models would indicate the wet weather pattern we have been experiencing here in July will continue. Above normal precipitation is expected with temperatures near normal. Temperature Normals and Extremes for August Monthly Temperature, Rainfall and Snowfall Extremes for August
* Historical weather statistics gathered from the National Weather Service's Denver / Boulder forecast office data archives. |
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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. 
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