Assuming it's even legal to shoot does where you're hunting, then yeah - I think you did the right thing holding your shot. 100 yards is near the max I'd be comfortable with a rifled shotgun. With a smoothbore 12-gauge, I'd normally wait on a 50-60 yard shot depending (of course) on how I'd done with it at the range.
As far as the rain is concerned... deer depend on scent first, hearing second, and sight third to alert them to predators. Rainy weather interferes with two of those three - by dampening scent and making the leaf cover on the forest floor quieter - so they will generally prefer to stay bedded down in heavy cover while it's raining.
I say generally because nothing is really a hard-and-fast rule with deer. If, say for example, the rain lasts for a day or two, they'll get hungry and they'll go ahead and eat, rain or no rain. They also worry a lot less about the weather when they're in rut, but the rut is pretty much over now so it shouldn't be a factor.
I find that rainy days are great days for stalking, but you have to know the area and know where to look. Generally speaking, the most productive places for me are along the bottom edges of brier thickets or heavy underbrush. They like to be able to see a good ways downhill when they're bedded down, but they also like to be close to a thicket they can dive into if they get pressed.