It was so cold in Pittsburgh that the ref's whistle froze

It was really cold in Pittsburgh for Sunday's AFC Wild Game game. Like, absurdly cold.

How cold do you ask? It froze a referee's whistle. Really.

During the third quarter, line judge Carl Johnson had to go to the sideline because his whistle wasn't working. At the time, it was 18 degrees with a 5-degree wind chill, which was apparently cold enough to freeze a whistle.

Johnson would eventually get the whistle to work, but it wasn't easy.