I'm still looking for the wind that keeps me from riding. I've cracked a trackstand with a 30mph crosswind and ridden in rain with similar winds and while it's a challenge, it's not impossible. The other night I was riding home and it was wicked hard to stick a line, but the weather said it was only a 15mph wind (and a headwind at that). I don't believe it though.
There were gusts up to 50mph one day this fall, but I missed out on the really nasty part. I was really looking forward to seeing what that's like.
Anyhow, I don't know. It's somewhere above 30, I guess.