My seats have been rained on before and are fine. They dried faster than the carpet. Only happened a few times though. Frankly, getting in after the gym has been more of an issue with the seats. I wish it would rain here just to clean them!
I've been caught miles away from my house in a downpour with the top off. Seats are fine. I just let them air dry the rest of the day in the garage. To be honest, I was more worried about the carpet and electronics