Dear Tom,

I hate muggy weather. How often does Chicago experience dew points in the 70s? When is the season’s first one likely to occur?

Courtney Becker  

Dear Courtney,

Summer is Chicago’s “sweating season” with the dew point reaching the 70-degree level an average of about 30 days each year. There are minimal occurrences of 70-plus dewpoints in May and September with the vast majority of the city’s muggy days arriving in July and August. In the most humid summers, the dew point has reached at least 70 degrees on more than 50 days, with the most, 53 in 2002. Last year the city logged 38 days. Oppressive dew points of 80 degrees or higher are rare in Chicago, with only six occurrences on the books since 1871. The city’s highest dew point was a sweltering 83 logged on a sauna-like July 30, 1999.