The first time I ever rode in one of these events, it was the Louisiana MS150. It is held in October every year, running 75 each day. Well, the second day it rained THE ENTIRE day. Let me tell you, THAT was miserable. Cold and wet are not a fun combination. I rode the whole day wearing a garbage bag.
At this point, if it rains in the morning and clears up in the afternoon, I'm A-OK with that.

Weather Underground has La Grange at 10% Sunday morning.
Repeat after me: "It is going to be a spectacular weekend. It is going to be a spectacular weekend. It is going to be a spectacular weekend. It is going to be a spectacular weekend...."