Living in the Pacific Northwest as I do, shooting in the rain is not just a possibility, but an inevitable occurence. I attended the McCord Air Force Base New Year's Day 3D Shoot Jan. 1, and sure enough, the rains came. I had a great time, but returned home with my arrows' fletching seriously the worse for having been soaked. I asked on the Howard Hill email list for anything that could be done and a couple of the guys suggested steam. I tried it and it worked. Here's how it went...
First, and this was before I got the steam suggestion, I dried the feathers with a hair dryer immediately on arriving home. That appeared to help a little, but at least they were dry. i didn't get back to them to try the steam until two days later. I picked up the arrows and noted that the feathers had returned to shape somewhat... better than they appeared immediately after the drying. I then put a pan of water on the stove, with tinfoil over the top (curl the tinfoil up so it doesn't touch the burner!). I poked a hole in the middle and rotated each arrow's fletching in the steam for maybe 15 or 20 seconds. You could see the feathers plump up and kind of come back together. I'd say they are about 90% as good as new.
This idea seems to work quite well, and makes me a lot more comfortable about using feathers in the rain. If you weren't aware of it, keep it in mind and give it a try.
Dick