Dear Tom,
Current weather observations are taken at O'Hare International Airport. Where were they taken 75-100 years ago?
—Chuck Maass, Oswego
Dear Chuck,
Chicago's official climate records date back more than 140 years to Oct. 15, 1870, when the U.S. Signal Service began weather observations at what is now 181 W. Washington St. Since then the site has relocated numerous times. Through 1925, weather observations were taken at a variety of downtown locations. From 1926 through June 1942, the site of record was on the University of Chicago campus. In July 1942 it was moved to Midway Airport and in mid-January 1980 it shifted to its current location at O'Hare. Sketchy weather records from Fort Dearborn in the 1830s and sporadic temperature records were taken from 1859 to 1870 but were lost in the 1871 Great Chicago Fire.
