Dear Tom,
Has there ever been a year in Chicago when thunderstorms occurred in all 12 months?
— Jim Kaplan, Joliet
Dear Jim,
Typically Chicago logs about 38 thunderstorm days each year with the vast majority occurring in the March to October period. However, thunderstorms have occurred in all 12 months and during the winter months, and they occasionally bring snow instead of rain. We had Chicago climatologist Frank Wachowski check the archives and he reported that there have been only two years since 1871 when thunder occurred in every month, 1950 and 1975. In 1950, the “out of season” thunderstorm days included one in January, two in February and one in both November and December. In 1975, there were a record four thunderstorm days in January, one in February and three in both November and December. In both years, all the winter thunderstorms produced rain and not snow.
