Dear Tom,
In what month is Chicago’s weather the quietest?
George Rogherston, Chicago

Dear George,
Nasty weather can occur here at any time of the year but, on average, August is Chicago’s most uneventful weather month. The path that low pressure systems and their associated storminess take shifts north into Canada in August.

Broadly speaking, storm systems that do affect Chicago in August are less frequent, move slower and are weaker than at other times of the year. Most August rainfall arrives with brief thundershowers. The percent of time that precipitation actually is in the air falls to its annual minimum in August, versus a winter maximum of 39 percent. But horrible weather has hit in August: the Plainfield tornado of 1990 and the northwest suburban flood of 1987, for example.