+1 - It's not absurd, it's also completely irrelevant. The only issue is whether the condition that caused the delay was within the carrier's control or not. Whether that is coded as "weather" or "airport conditions" is irrelevant.

It all comes down to commercial reasonableness. UA could certainly have paid someone to stand around all night, opening and closing the cabin doors, but that's not really a reasonable task. After all, it gets cold all the time, but aircraft doors freezing shut such that they cannot be opened in short order is a pretty rare occurrence (below the Arctic Circle).