Dear Tom,
What is the value of the highest air pressure reading ever recorded in Chicago?
Allen Peerlinson

Dear Allen,
In official weather records dating from Nov. 1, 1870, to the present, the highest air pressure reading recorded in Chicago stands at 30.98 inches of mercury. The date was Feb. 16, 1989, and the location was O’Hare International Airport. High and low temperatures that day were 26 and 8 degrees and there was no precipitation.

Chicago’s lowest air pressure reading occurred on March 12, 1923, when the barometer bottomed out at 28.70 inches. Temperatures that day were 41 and 31 degrees, and 0.67 inches of precipitation fell. That included 0.2 inch of snow.

The difference between the highest and lowest air pressure readings is 2.28 inches of mercury, and that represents a change in elevation of 2,160 feet.