Dear Tom,
Our 7th grade geography class is learning about air pressure. What are Chicago’s extremes of barometric pressure?
Clay Watkins, Scullen Middle School, Naperville
Dear Clay,
Since 1871, Chicago’s barometric pressure readings have varied across a range of 2.28″ of mercury, the equivalent of the drop in air pressure one would encounter climbing from sea level to the top of a 2,160 foot mountain. The city’s highest barometer reading of 30.98″ occurred on Feb. 16, 1989, a sunny, cold day with a high of 26 (degrees) and a low of 8 (degrees). The all-time lowest pressure reading here of 28.70″ was recorded on March 12, 1923, a chilly, stormy day with 0.67″ of precipitation that fell as both rain and snow. Worldwide, barometric pressure extremes range from a 2001 high of 32.06″ at Tosontsengal, Mongolia, to a low of 25.69″ measured northwest of Guam in the eye of Typhoon Tip in 1979.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
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