Back in the day, NFL coaches didn’t give a crap about things like the weather. Players were expected to show up, suit up, and give it their all whether it be in cold, heat, humidity, or shoe-sucking mud. Many old school coaches believed practicing in adverse conditions better prepared players for playing in them. Northern teams that played home games outside in December had a marked advantage over a team flying in from a tropical locale, and the heat often wreaked dehydration havoc when those northern teams visited hot muggy Florida in September.
Nowadays, with nearly every team facility sporting an air-conditioned practice bubble, and many teams sporting climate-controlled domes, you would be excused for thinking the NFL wanted to play every game in 72-degree, dry calm weather.