I saw a list of coldest games. The original Ice Bowl between Green Bay and Dallas was coldest. The Chargers Bengals game was secong.
If you account for wind chill, the Freezer Bowl (Chargers-Bengals) was the coldest at -59F.
Forrest Gregg was an offensive tackle for the Packers in the earlier one, and head coach of the Bengals in the latter. That's a rather frigid distinction.