Dear Tom,
Is there any day in all the days of the year on which precipitation has never fallen in Chicago?
— Manny Boben, Chicago
Dear Manny,
Precipitation falls so frequently here, and Chicago’s precipitation records cover such a long period of time, that rain or snow has been measured on every day of the year. That includes Feb. 29, leap day.
Chicago’s official precipitation records began on Nov. 1, 1870 , and cover a period of almost 147 years. We scanned the data from 1871 through 2016
(146 years) and found that measurable precipitation (defined as 0.01 inch or more) has fallen on 18,187 out of a possible 53,326 days, or
34.1 percent of the days. The “wettest” days of the year turn out to be March 19 and 26, each with 69 days of precipitation, or 47 percent of the days. July 1 and Aug. 31 are “driest” with 29 days, or 20 percent of the days.
