Drop em in their tracks and you will not have to worry about tracking.
Might go for a shoulder shot so that you instantly take out both legs rendering him incapable of running away thus not having to worry about tracking. You could also try for a neck/head shot if you feel you are proficient enough to make that kind of shot.
But other than that I can't help you I have never had the opportunity to hunt in the rain so I have never had to worry about it. Good luck and I hope you get one.