I’ve seen Boyd ride multiple horses through a Nor’easter at Jersey Fresh (when I was crazy enough one year to go as a spectator in that weather; it didn’t seem that bad when I left, famous last words). His horse lost a shoe in front of us and my friend fished it out of the muck to give it back to a steward.
I wouldn’t think poorly on any rider who scratched because of weather, though. Every rider knows his or her horse best and personal level of skill.