Solvang double century 2006 - probably 160 of 200 miles in the rain, beginning about mile 20. Davis 400k last year - most of it in the rain, let's just leave it at that. (The only really nice weather was the first part of the return where V joined me.) 600k in 2006 had only 15 miles in the middle in the rain, but so hard I thought I wouldn't be able to breathe.

It's definitely harder to start in the rain or when you know rain is imminent than to keep going if it starts raining in the middle.