I've had it happen at Bristol a few times, even had snow! My most memorable rain delay was at the 1972 Indy 500 on Pole Day qualifying. We sat in the rain all day, until about an hour before time was up, when the sun came out. There were even three tornados that passed within sight of the track. At that time if just one car made a complete run, the first day was over, the car was on the pole, and everyone else was now a second day qualifyer. The real bad deal was that we had to buy another ticket too. The track became dry with just enough time for one car to make a run, and it was A J Foyt. On his second lap his engine let go right in front of us in turn one. Everyone jumped up and cheered because we could now use our tickets for the next day.
A sad note, just as we sat down on Sunday, a car hit the wall right in front of us in turn 4, and the driver was killed. I cannot remember his name, he was not a regular Indy car driver. I knew he was dead as soon as the car came to a stop. His helmet was fractured! My wife didn't want to go to the 500 after seeing it, but we had spent the money, so she went.