At the time of this writing, Madison is in its 6th straight day of temperatures at or above 80F and it is likely we will have one more to reach seven in a row.
As recently as 2022, we have had 13 of the first 21 days of September reach 80F or higher. In fact, it was just last year that we set the all-time record for longest consecutive streak – initiated within September – of 80F or warmer days at 12 straight, running from September 10 – 21! This also happens to be the longest consecutive streak of such days in September ever in Madison (1978 and 1981 both had 11 straight 80F September days). It may have occurred to you that this mid-September heat is a bit unusual – though it is far from unprecedented.
Interestingly, the earliest day on which Madison has ever recorded its last 80F day of the year was September 2, 1977 (and 2020). The all-time latest 80F day in Madison’s history was, again, last year on October 29.
The average last such day (since 1939) is September 29. Within the 85 seasons (not including this one) since 1939 there have been 61 times when the last 80F day occurred after September 21 (the average date of the autumnal equinox). Thus, summer-like warmth is a common feature of early fall in southern Wisconsin.
So, we hope you have enjoyed the brilliant sunshine, light winds and dry conditions that have set in over us these last few days – we all know it won’t last – though, as the foregoing attests, there may still be time for another visit from summer before it is officially a thing of the past.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
