What year hosted the most 80-degree-plus days in Chicago?

Dear Tom,
I prefer to judge a warm season by the number of days of at least 80 instead of 90. What year hosted the most 80-degree-plus days?
— Peter W., Mokena
Dear Peter,
Days when temperatures reach at least 80 are generally ideal for most summer activities, including swimming. The city’s long-term average is 69 days, but that includes the period from 1871-1942, when the official thermometer was located near Lake Michigan. When counting just the inland years after 1942 at Midway and then O’Hare, that number jumps to 82. The year with the greatest number of days of at least 80 is 2005 with 103, closely followed by the runner-up years of 2007 and 1953 with 102. In contrast, 1875 logged the fewest with just 26. There were nine years with less than 40 days, all occurring earlier than 1925 in lakeside locations.