At this time in September, the hottest days are behind us– but that has not always been the case.
There was quite a heat wave around Labor Day. The National Weather Service office had two consecutive 90° days, with a September record 95° a week ago Monday (Sept. 4).
In recent times, hot temperatures in September of 90° or above have been confined to the first 10 days or so of the month. For instance, the NWS’s latest 90° high was on Sept. 11, 1998. On the other hand, Houghton’s latest 90° day was on Sept. 15, 1939, while it hit 90° in Munising on Sept. 18, 1955. Residents in Iron Mountain perspired under a 90° temperature as late as Sept. 22 in 1908. In Marquette, the latest 90° is over a week later– on the last day of the month, Sept. 30, in 1897.
Remember, the greatest U.S. summer heat waves occurred during the 1930s. In the U.P., the greatest, latest September heat waves were also in the 1930s. Marquette (96°, 98°, 94°) and Munising (91°, 97°, 93°) both had three consecutive days with highs in the 90s Sept. 10-12, 1931. Iron Mountain (Sept. 8-11: 95°, 95°, 96°, 97°) and Ironwood (Sept. 9-12: 93°, 96°, 92°, 90°) racked up four straight days in the 90s in 1931.
Here’s more proof it was hotter in days gone by. Records at the NWS only go back to 1961. There, only six calendar days in the month have record highs in the 90s. Houghton, where records go back to the turn of the 20th century, has 10 calendar days, Munising has 16 days, Iron Mountain has 18 days, and Marquette– where records go back to the Civil War– has 24 calendar days in September with highs in the 90s.
While 90s are not anticipated, it does look like above average temperatures will take hold again in the longer term. At the same time, an extended dry spell is expected to last late into the month.
