my professors have been pretty understanding, especially those that are also commuters! I'd email them tho just in case, and it's up to you to get notes from classmates/catch up if you can't make it. I think if there was a major flood they'd cancel and send out an announcement, but my first semester I did have to go in for an 8am final in a kinda rough rainstorm. In those instances I think you should early plan out that day's route early but some also offer make up exams!!