After a little bit of digging, I found the local NWS Office’s list of 100 degree days in Denver since 1872 – a 140 year history. I’ve graphed number of occurrences by year:
The data is valid through the 28th of July, 2012. As I’ve stated in previous posts, the previous yearly maximum number of occurrences took place in 2005 with 7. So far this year, the temperature has exceeded 100°F 13 times. At this point, I do not expect the NWS to record another 100°F day during the rest of this year. While it has been warmer than normal in Denver, the North American monsoon season has kicked into gear, which suppresses daily maximum temperatures due to cloud formation. The afternoons cannot get as warm with widespread, thick clouds as they could prior to the monsoon when the sun warmed the ground throughout the day.
Note that while 100°F day incidence appears to be increasing, I am not making any claim as to the statistical significance of such a development. The linear trend (not shown) over the entire dataset is slightly positive, but these events are too rare from which to draw robust conclusions.
That said, the average temperature through the 28th of July in Denver is 78.9°F. The Denver/Boulder NWS Office has the top-10 warmest Julys list:
10 WARMEST JULS
77.8 1934 #
76.9 1966, 2003
76.7 2000, 2001
With only three days remaining, July 2012 has a very legitimate shot at the hottest July in 140 years’ of record-keeping. If the average temperature remains near 78.9°F, 2012 will also beat out 1934’s 77.8°F by over 1°F!! And while the 1930s were a very warm decade, note further that 5 of the warmest Julys on record occurred during the 2000s.
What is the `#` symbol in the table? The NWS notes this:
# Warmest Month in Denver History.
If July remains anomalously warm from today through Tuesday, July 2012 will be the warmest month in Denver history. This follows on the heels of the hottest June on record: 75°F, which beat the old record of 73.5°F (June 1994).