By themselves, 20-30 mph winds, torrential downpours and ~30 degree windchills are not that bad in isolation.
But realistically, you are looking at a lot of volunteers no-showing in an environment where 30,000 are going to be at risk for some pretty rough conditions. I feel like the underwriter of the event has be pushing hard at this point.
At a certain point one has to ask, what is the race trying to prove?
Dude, please don't ever google The Barkley Marathons - you'll have an aneurysm for sure.