Prior to about 1940, June 19 used to frequently be a hot day in the US, but June 19 temperatures have been declining since the 19th century. One notable exception being 1988, during the week when James Hansen gave his testimony to Congress predicting increased summer heat.
The Midwest has been over 100 degrees on June 19 seventeen times since 1895. All occurred more than 20 years ago, and all but three occurred more than 60 years ago. On this date in 1936 it was 107 degrees in Missouri and 106 degrees in Illinois.
These maps show US temperatures on five of the hottest June 19ths.