Chicago experienced its hottest summers (June 1st through August 31st) in 1955 (24.7°C), 1995 (24.6°C), and 2012 (24.5°C). As of Thursday, we've had an average temperature of 24.6°C—already tied for 2nd place. If the 10-day forecast holds, we will end the summer a week from Monday with an average temperature of 24.7°C, tying the 1955 record.
WGN-TV's Tom Skilling explains why we have this situation, despite none of the three months of 2020 making it into the top 3. (Hint: all three made it into the top 5.)
How is it possible this summer ranks among the top tier of warmest summers to date here? What about the deadly heat in summer 1995. Or how about the scorcher of a summer in 1988 with its 47 days with above–32°C and seven days of above–38°C?”
1995’s July heat wave was historic and responsible for the greatest loss of life on the books produced by a natural disaster in the Chicago area–but it occupied a week’s time. It was a single hot period and not reflective of the average temp over the full season through August 19 which came in under this years 24.6°C average to date.
It’s true summer 1988 produced the greatest number of above–32°C and above–38°C of any warm season since official records began in 1871. But summer 1988 produced also produced historic drought. Moisture was so limited in the Summer of ’88 that the drier than normal atmosphere allowed nights which cooled more than usual from the broiling daytime highs. So when the comparatively “cool” nights were averaged with the hot daytime highs, the average summer temps through August 19 came in well below this year’s 24.6°C to date.
So, Chicagoans, neither you nor your air conditioning is wrong. This summer has suuuuuuuucked.
Also, starting in January, we will have new climate normals. Every 10 years climatologists crunch the previous 30 years of data and produce a new set. The 1991-2020 set will almost certainly have higher temperatures and precipitation amounts for most US locations than any previous set, just as the 1981-2010 set did. Early in 2020, meteorologist Becky Bolinger ran 29 years of data and discovered that only one county in Iowa had fewer above-average monthly temperatures than below-average from 1991 onward. Every other part of the US experienced rising average temperatures.
In other words: welcome to the new normal, thanks to human-caused climate change.