Denver’s June-August Recap; Welcome to (Meteorological) Fall

Although the calendar won’t tell you it’s fall for another few weeks, meteorological fall began on Monday, September 1st. Meteorological fall runs from September 1st to November 30th.

Summer Temperatures 2014
It certainly wasn’t the coolest summer Denver has ever experienced, but also a far cry from recent years, as the region overall experienced near-normal temperatures over the last three months. According to Climate Central, Denver ended up somewhere just right of center in this chart of coldest to warmest summers on record.

Official temperatures (recorded at Denver International Airport (DIA)) were very close to normal for June and July, but notably cooler than normal in August. June ended -0.1 below normal for the month at DIA, while July ended 0.3 degrees above normal. August, however, was an impressive -1.9 degrees F below normal! In general, northeast Colorado saw temperatures at or slightly below normal this summer, while southwest Colorado was at or above normal.

90 degree days were hard to come by over the last few months, at least when compared to recent years. Denver recorded 27 days at 90 degrees or above between June 1 and August 31. That’s down from 47 days in 2013 and 64 days in 2012. Not coincidentally, this is the fewest number of 90 degree days during the three month period that Denver has seen since 2009.

Precipitation
A similar story played out for precipitation. During the June through August period we saw generally wetter than normal conditions across northeast Colorado, with drier than normal conditions across the southwest corner of the state. DIA recorded 2.73 inches of precipitation in August, which is 1.04 inches above (162% of) normal.

August was very wet for much of the Rocky Mountain west. Northern Colorado ended the month well above normal, as did portions of Utah, Nevada, Idaho, Wyoming, and Montana. There were even a few spotty locations in California that recorded some rain…

NWS summer 2014 precipitation totals

For the summer months (June - August) we see that the core of precipitation shifted a bit further east than it was over the last month, with much of eastern Colorado seeing near to above normal precipitation through the period.

Some drought relief
Colorado took a step in the right direction this summer when it comes to drought relief as well. According to the U.S. Drought Monitor Colorado started the summer with 44.71% of the state not experiencing drought conditions, and that number now stands at 60.21%. While it would have been nice to see more improvements in hard-hit southeast Colorado, there have been marginal improvements there as well. As of May 27, 2014 more than 12% of the state (all in southeast Colorado) was experiencing Extreme to Exceptional drought, that number is now down to 2.67%, with no drought conditions classified as Exceptional in the state.

Drought Monitor

September
The month of September is typically fairly quiet for eastern Colorado. Our monsoon season comes to a close during the month, and the days tend to be warm and nights are cool. While nothing quite beats a perfect September day in this state, the month can also offer extreme weather. Next week will be the one year anniversary of last year's historic flood event across northern Colorado.

Related: High Water | Colorado Floods, 2013

September is Denver’s fourth warmest month of the year (behind July, August and June), it is also the first month of the snow season for the city. According to the National Weather Service, the warmest temperature on record in September for Denver is 97 degrees F, while the coldest on record is 17 degrees F.

While September averages 1.1 inches of snow for the month (long term average from 1882-2014), the city has not seen any snow in September in 14 years. In 2000 0.2 inches of snow were recorded at DIA, and in September 1999 3.1 inches fell. Here’s a look at the snowiest Septembers on record in Denver:

  • 17.2 inches 1971
  • 16.5 inches 1936
  • 12.9 inches 1959
  • 11.4 inches 1895
  • 8.7 inches 1985

Needless to say, there is no snow in the forecast this week with daytime temperatures primarily in the 80s, with the exception of Wednesday, when highs may soar well into the 90s, perhaps even flirting with the record high for the date of 95 from 1995.

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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