The National Weather Service says an approaching cold front from the northwest should collide with a warmer and more humid mass of air, bringing with it a 70-percent chance of rain for race day.
The race is set to begin shortly after 1 p-m Eastern. If it's rained out or halted before 101 of the 200 laps are completed, it would be rescheduled for Monday when the chance of rain is 40 percent.
By the way, the last complete washout of the Indy 500 was 1997, when the race was postponed to Monday. It was stopped after 15 laps and completed Tuesday.