The NFL championship game was played the last few days of December going back to the late 1950's
"the Greatest game ever played" NFL Championship game between the Giants and Colts was played on December 28, 1958.
The "Ice Bowl" was played December 31 and it was -13 degrees in Green Bay.
Not as late as games are now, but certainly not fall weather.
So for the past 65+years winter weather has been a part of pro football.