October 21, 2016
By Tom Skilling
Ask Tom: (click here) How much does weather vary throughout the Chicago area?
Dear Tom,
How much does weather vary throughout the Chicago area? I know the first frost is earlier in the suburbs.
- Lawrence Dayte
Dear Lawrence,
The weather does indeed vary greatly across metropolitan Chicago for a number of reasons. Proximity to Lake Michigan is important, moderating temperatures in the winter and cooling daytime readings in the summer. It also causes lake-effect snow in the winter. Also, there is the "heat island" effect, in which urbanization keeps temperatures higher in the city, especially on calm, clear nights. Not as obvious is the expansion of suburban Chicago; there is more space for varying weather events.
As for the first freeze (frosts are not recorded), the averages for the Chicago area vary by more than a month, from about Oct. 3 in the coldest suburbs to Nov. 5 in the Loop.
