The closest active USHCN station to Grand Rapids is at Alma which recorded it’s hottest temperature of 108F on July 14, 1936. Alma hasn’t been over 100F since 2001.
Alma has recorded 1,751 days over 90F since 1887, 74% of which occurred before 1980.
Summer afternoon temperatures have also plummeted in Indiana and Tennessee.
Temperatures at Bloomington, Indiana also peaked on July 14, 1936 and the frequency of hot days has plummeted.