I believe most animals react to changes in barometric pressure. This is especially true when the pressure is falling, which usually indicates a big change in the weather. If it's a sunny, pleasant day, the barometric pressure will be high. When a storm begins to move in, the pressure will always drop. Most animals, especially deer, realize this and will begin to feed more often before the storm arrives.

Conversly, when the storm moves out, the pressure will again rise. Changes in pressure again will usually increase deer activity.
I have found the best time to be in the woods is immediately after a storm, either heavy rain or snow. As the storm moves out and the barometric pressure again begins to rise, deer that have been bedded during that nasty weather will be on the move again. Feed will usually be their highest priority.

Hope this helps. Just my .02