Dear Tom,
According to Koppen’s climate classification system, Chicago’s climate is called “continental warm summer.” Are there any other places that have the same climate classification?
Roger Smith, Oakland, California

Dear Roger,
The Koppen classification system suggests that Chicago shares climatic similarities with New England, the central Great Plains, Bulgaria and portions of South and North Korea and northern China. The Koppen climate classification system was published in 1918 by German climatologist Wladimir Koppen. Faced with a lack of adequate observing stations, Koppen used vegetation to approximate climatic conditions in data-sparse areas of the world. The system defines five major climatic zones. His system has been updated occasionally, including changes by G. Trewartha.