... this official statement from an NFL Spokesman:
As is our standard procedure, we are monitoring the forecast and will stay in close communication with the weather service and both clubs. As per NFL policy, in the case of inclement weather, specifically lightning, the referee has the authority to determine when it is appropriate to suspend play and clear the teams from the field. The NFL Game Day Operations Center is in constant communication with the referee and the on-site NFL Football Operations representative in order to communicate forecasts and severe weather warnings. These forecasts and warnings are issued by a third-party meteorological service specifically contracted to monitor inclement weather that could affect NFL games.
... the system is heading to Cleveland to catch the game.
"The latest data I’m seeing this morning is calling for widespread five plus inches of rain, with locally seven plus inches," according to Tanchak. "The heavy rain will start late Saturday night. So that means all day Sunday and Sunday night we are looking at continuous heavy rain. Winds will be gusting up to 40 mph at times."