Turkeys have several air sacs throughout their bodies that can tell the slightest change in barometric pressure, thus warning them of an upcoming storm. If your local weatherman is saying a storm is coming, your best bet is to hit the woods a couple of days before the storm gets there, because the turkeys will be feeding like crazy in anticipation. I have had lots of success with this. But like other posters mentioned, if it is lightly raining, it won't bother them, but they won't gobble as much if it is raining/cold/cloudy weather.