Egads...! they may get lucky if rain stops play...
Ah... tea-time... 
Neither rain, snow, sleet, fog nor subzero temps stop the game. Lightning can, for obvious safety reasons.
The two classic cases in point:
The "Ice Bowl": NFL Championship game between Green Bay Packers and Dallas Cowboys, Dec. 31, 1967. The official game-time temperature was -13°F / -25°C, with a wind chill around -48°F / -44°C. Using the new wind chill index put into use in 2001, the wind chill was -36°F.
The Fog Bowl: that was the name given to the December 31, 1988 National Football League (NFL) playoff game between the Philadelphia Eagles and the Chicago Bears. A heavy, dense fog rolled over Chicago's Soldier Field during the 2nd quarter, cutting visibility to about 10-20 yards for the rest of the game.
And of course, innumerable games played in snow heavy enough that the line and yard markers had to be periodically cleared so the players and officials could see where they were.
