August 13th afternoon temperatures have plummeted in the US over the past century, as has the frequency of hot days.
On this date one hundred years ago, almost the entire US east of the Rocky Mountains was over 90 degrees.
On this date in 1936, the average US afternoon temperature was 93 degrees. Kansas was 119 degrees, Oklahoma was 116 degrees, and Texas was 114 degrees.
On this date in 1944, two thirds of the US was over 90 degrees, and there were 100 degree temperatures coast to coast.