DENVER — Cool mornings in the summertime are one of the things that makes living in Colorado so great. It’s a time for people, animals, plants and even buildings to recover from the heat of the previous day.
But at least down on the Front Range and other lower elevated places, the mornings have not been as cool in recent years.
The lowest temperature in Denver on Monday was just 72 degrees, a record for Aug. 21. And Tuesday morning’s low was 73 degrees, that will also be a record unless it cools below 69 degrees before midnight, which is not likely to happen.
That 73-degree low temperature could tie the all-time warmest low temperature in Denver history, depending on how you look at the data.
The official record book shows two temperatures in the summer of 1881 as Denver’s warmest lows – 77 and 76 degrees.
But those measurements are suspect.
We don’t know if those temperatures were truly measured at the coldest minute of the day. There were markers on old mercury thermometers that could record the high and low levels of the day, but they would have to recent frequently, and it's not known if the time of the measurements were recorded.
And from 1871 to 1890, weather measurements were not even taken by meteorologists. It was the responsibility of soldiers with U.S. Signal Service.
The most reliable temperature records in Denver start in 1948 when the temperature was measured every minute of the day and at a reliable location away from buildings. And we know those instruments were properly shielded from solar radiation.
Using that data, the 73-degree measurement would tie the record from 2003.
The temperature data also shows that 70-degree lows are becoming more common. From 1948 to 1990, there were five 70-degree lows in Denver and since 1991, the low temperature has been 70 degrees or warmer 23 times.
And before this year, the low temperature in Denver was 70 degrees or warmer after Aug, 20 only one other time. That was August 30th in 2013. There's never been a low that warm in September.
Fort Collins
A climatologist with the Colorado Climate Center said there is some data from the old weather station at Colorado State University that might corroborate the 1881 temperature anomalies. Peter Goble said he found an entry from 1881 that said the warmest low temperature in Fort Collins was 77 degrees that July.
So perhaps there was something strange causing unusually warm low temperatures that summer on the Front Range.
The official verified record book for Fort Collins kept by NOAA shows that the warmest low temperature ever recorded there is 76 degrees on Jul. 31, 2006.
Fort Collins did not break a record warm low on Monday as the temperature dropped all the way down to 57 degrees there. And Tuesday mornings low of 60 degrees will also come up just short of a record.
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