weather.gov seems to support this claim.
https://www.weather.gov/arx/heat_jul36
1936 record july temps:
All-Time Records Set in July 1936
Location Temperature Date
Decorah, IA 111F July 14
Fayette, IA 110F July 14
New Hampton, IA 110F July 13
Mondovi, WI 110F July 14
Richland Center, WI 110F July 14
Rochester, MN 108F July 11 & 14
La Crosse, WI 108F July 14
Lancaster, WI 108F July 14
Viroqua, WI 108F July 13
Hatfield, WI 108F July 14
Osage, IA 107F July 14
Friendship, WI 106F July 14
Grand Meadow, MN 106F July 14
Mather, WI 106F July 14
Neillsville, WI 106F July 14
Sparta, WI 106F July 13
Medford, WI 104F July 13