As you can see from the satellite image this morning, there are quite a few clouds over Illinois and Missouri that are moving east-northeast. Most of the morning at Indianapolis will have broken to overcast high clouds, but they will gradually be decreasing. I think there will be more sun than clouds for the majority of the race. This will warm temperatures into the lower 80s. There will be a south wind at 10-15 mph during the race, which will provide a tail wind on the back stretch and a head wind on the front stretch.
I expect that clouds will increase again after the race is over, and there could be a few light sprinkles around through the evening. The chance of rain will increase overnight, with showers and thunderstorms likely late at night and into Monday morning.
Enjoy the race.