I've killed a schit load of deer in the rain. I don't think it affects them that much, they still have to eat. I think the only time it affects them is if it's a driving torrential downpour with 30 mph winds. I'm not a fan of it though, because you can't hear anything and you can't rely on a blood trail if need be. Better make a good shot. Like others have said, if you can be out there when a cold front moves through and it stops, the ones that were hunkered down get up and move.
I've learned to beat the rain with a good rain suit, a tree stand umbrella, good boots, and gloves with Gortex. The tree stand umbrella is worth it's weight in gold. I've got 3 of them. About 20 years ago for Christmas, my daughter who was about 10 at the time, gave me one as a gift. To show my gratitude to a little kid, I told her how great that was and how much I loved it. However, in my mind, I was thinking that this was another useless hunting gadget that I probably would never use. I put the thing down in the basement with the rest of my hunting stuff. Because of my stupidity, I never took it out of the box for several years. Then came an opening day and it was going to pour down rain all day. I thought about that umbrella and dug it out of hiding and used it. It's probably one of the best hunting gadgets anyone has ever come up with. I highly recommend them. If it's windy, they don't work so well. I've tried them in the snow, but snow never falls straight down, and it makes noise when it hits the nylon.
I've got the Porta-Roofs, but it looks like they are out of stock.
https://www.amazon.com/Allen-Instant-Roof-Treestand-Umbrella/dp/B06X6JGLT1Here's another one from Big Game Treestands. Looks about the same.
https://www.cabelas.com/product/Big-Game-Treestands-Pop-Up-Umbrella/1619030.uts?slotId=0
