“Hotter than the Fourth of July” (very hot)

Entry in progress—BP
 
“Hotter than a firecracker on the Fourth of July” and “Hotter than noon on the Fourth of July” are related sayings.
 
Newspapers.com
3 July 2009, The Daily Oklahoman (Oklahoma City, OK), “Some cool statistics sparked by the Fourth” by Bryan Painter, pg. 16A, col. 1:
You’ve probably heard them for years, the Fourth of July cliches.
 
“Hotter than a firecracker on the Fourth of July.” “Hotter than noon on the Fourth of July.” And the generic “Hotter than the Fourth of July.”