Why is the temperature at Midway Airport usually higher than at O’Hare International Airport even though they are not that far apart?

Dear Tom,
Why is the temperature at Midway Airport usually higher than at O’Hare International Airport even though they are not that far apart?

Mark Gaffney,
St. Charles

Dear Mark,
Midway Airport lies 16 miles southeast of O’Hare International Airport, but O’Hare is a more outlying location than Midway. It’s certainly true that O’Hare is not rural because there is considerable “city” development that extends several miles outward from the airport. However, Midway sits much more to the interior of metropolitan Chicago than does O’Hare and consequently is more affected by the “urban heat island” of the city area.

In the period from 1959 through 2017 (the years for which complete temperature records are available at both airports) , the average temperature at Midway was 51.2 degrees and at O’Hare 50.0 degrees. Midway is, on average, 1.2 degrees warmer than O’Hare.

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