Will the imsa races run in the rain?

Rain yes. Lightning no

IMSA does run in the rain. They will stop a race due to an excessive amount of water though.

Yes. Unlike NASCAR, IMSA comes equipped to run in the rain. The only time that I have seen a race stopped due to excessive water was a few years ago before the resurfacing of the track. There was so much standing water and the visibility was so bad that it was dangerous to race.

Yes

They will indeed, however, if it becomes a monsoon they may delay it (for safety reasons) and resume when it lightens up....