As I recall, the temperature was in the 60s, but the main asset was not having the sun glaring on the ice. The 2019 Winter Classic at ND, which I attended, had ideal weather for the event -- cloudy, dry, and in the 30s. That was similar to the weather in Arlington for the Cotton Bowl three days earlier. It's very unlikely to be in the 70s in Dallas on January 1, but the main things to avoid are the extremes of bright sunshine and rain.