Dear Tom,
You have said Chicago’s daily normal temperatures were smoothed so that they change by no more than 1 degree per day. How much variation would there be if they were unsmoothed?
— Brian Dunne, Westmont
Dear Brian,
You have stated the “smoothed” situation correctly. Chicago’s daily normal temperatures at O’Hare International Airport (calculated from the 30 years, 1981-2010) range from 23 degrees (the average of a day’s high and low temperatures) in mid-January to 74 in July. The unsmoothed averages range from 20 degrees to 77, and they fluctuate by up to 4 degrees per day. The greatest fluctuation, 4 degrees, occurs on three occasions — from 23 to 27 degrees on Jan. 21-22, from 50 to 54 on April 23-24 and from 23 to 27 on Dec. 26-27. Fluctuations of 3 degrees occur an additional 13 times.
