Dear Tom,
What is Chicago’s record for the largest temperature swing in a very short period of time?
Eleanor Whitcore, Evanston

Dear Eleanor,
The greatest temperature shift in a short period of time in Chicago weather history (from Nov, 1, 1870, when records began, to the present day) is a 22-degree plunge. It occurred on May 9, 1963, at Grant Park. It began with a temperature of 84 degrees, recorded at 1:47 pm, and ended 150 seconds later when the thermometer had dropped to 62 degrees. That 22-degree temperature drop in 150 seconds is Chicago’s largest documented short-term temperature plunge. Other larger temperature drops have taken place, but they have taken longer periods of time to occur. The two and one-half minute temperature plunge mentioned above still holds the short-term record.