I prefer to avoid hunting in the heavy rain because deer don't seem to move nearly as much, and I don't want to risk the blood trail washing away. I really like hunting in light rain that's supposed to let up during daylight, as I find deer move a ton right after the rain, and I'm able to sneak into my spot with very low impact. As others have said, shot placement is critical, and I wouldn't shoot at any animal unless I considered it a "slam dunk" kind of shot. Along those lines, you might want to sit out the opener if you haven't shot your bow in the rain/when the strings are wet. Even at 20 yards, shooting a wet arrow with wet bow strings can change the point of impact by several inches, which could lead to a bad hit and a long, washed-out blood trail. If you've practiced in those conditions and know where to aim/how to adjust, then I say go for it!