How often does a day’s actual high and low temperatures equal the normal high and low temperatures for that date?

Dear Tom,
How often does a day’s actual high and low temperatures equal the normal high and low temperatures for that date?
— Bill Wilson, Dyer, Ind.
Dear Bill,
It doesn’t occur very often. We used Midway Airport data for the period 1929 through 2017, the years for which complete high and low daily temperatures are available. That’s 88 years of data. A computer check of observed daily high and low temperatures against Midway’s normal daily high and low temperatures revealed only 83 occurrences on which all four numbers were exactly the same, or slightly less than one day per year.
Chicago’s temperature climate usually consists of swings (sometimes rather large swings) around the daily normals, and it’s not often that a day’s high and low readings are exactly equal to the normals on a given date.
The most recent occurrences on which a day’s high and low temperatures were identical with the normals on that date:
Aug. 20, 2016: high 82, low 66
Aug. 6, 2016: high 83, low 67
Jun. 25, 2015: high 83, low 65
Aug. 1, 2014: high 83, low 67
Dec. 29, 2012: high 32, low 20
Dec. 11, 2012: high 36, low 24
Apr. 2, 2011: high 54, low 37
Apr. 12, 2011: high 58, low 41
Jan. 28, 2011: high 32, low 18
Nov. 16, 2010: high 48, low 34
Jun. 18, 2009: high 81, low 63
Oct. 18, 2006: high 62, low 45
There are no “favored” times of the year for these occurrences; they tend to occur about equally, and randomly, during all seasons.

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