A few guys have mentioned the period just before and just after a rain... this is good info. If I know the weather is going to change I try to be out hunting before it does. Just before a Weather Front moves in deer become more active and your odds go way up. Conversely the same applies to the passing of the front, although the activity is usually not as frenetic, the game will move immediately when the rain quits as well.
I would like to qualify with regard to severe weather... electrical storms (lightning) and high winds are not conducive to hunting success or safety!