Dear Tom,

What is the warmest month in St. Charles? I have a small bet with a friend.

—Matt Dowling, St. Charles

Dear Matt,

July is the warmest month, on average, followed by August and then June. Chicago area temperatures are complicated by the city’s proximity to Lake Michigan. The lake tends to cool afternoon locations near the lake in the summer (with an opposite effect, warming, during the winter). St. Charles, located about 35 miles west of downtown Chicago, experiences less summertime cooling than areas closer to the lake. Average July temperatures at St. Charles are 84 degrees (average high) and 63 (average low). August, the second-warmest month, averages 82 degrees and 61; June, 81 and 58 degrees. In about one year out of five, August will be warmer than July.