Dear Tom,
As summer begins to wind down, when can we expect our first high temperatures
below 70 degrees? How about back-to-back days of sub-70-degree highs?
-Matt Balitewicz, East Chicago, Indiana
Dear Matt,
A few "cool" summer days (defined as days whose maximum temperature fails to break
out of the 60s) occur all through the summer, but not very often.
A scan of 80 years of daily highs registered at Midway Airport during the last week of
July and first week of August indicates that sub-70-degree highs occurred only 19
times, or one day out of 59. That frequency increases to one day out of 28 at the end of
August and one out of two by the end of September. The average date of the city's first
sub-70 day in the autumn is Sept. 10, and the first back-to-back sub-70 days can be
expected a week later, Sept. 16-17. A string of three such days is likely by Sept. 22-24.
