I've always had pretty good success in the rain. Knocks down scent and noise a little and, well, I just love rain....back in the day working construction in the field, a rain out meant I could slip off to the deer camp and get in an extra hunt.
Unless its raining buckets, it shouldn't be too much of an issue. Maybe get on the trail sooner so the blood isn't washed too bad. Here again, you're less likely to spook and drive them in the rain.
As an aside, we had a nasty drought here and they had some video on the news a while back of some deer (fawn/yearlings)freaking out in the rain. No clue what it was....Point is, rain messes with deer's habits and senses to an extent.