I say "just think like a deer."

Deer do not like it when they cannot naturally use their senses to detect danger. Typically when the storm is getting with it, downpour, thunder, and lightning, the deer will tend to be mostly immobile. They can't hear as well cause of the rain and the thunder. Same with visibility. If it's raining really hard or it's extrememly foggy, I find that deer are less mobile in these conditions. A heavy rainfall can also mask the odor of some potential dangers.

A light rainfall or a mist? Has very little to no impact on deer movement that I can detect.