Rain or shine, I match my calling to the birds. If they are vocal so am I. If not I stay quiet. When a tom gobbles to my call I count the seconds between the time I call and he answers. Then I wait that long before I call again. That keeps me from over calling or not calling enough. On a hot bird the times will keep getting shorter. I keep that up until I have to move on him or I kill him.
The fields are also a good bet in the rain. When a turkey gets soaked they're miserable just like us. They'll get out in the open and just stand there. I think the rain makes it too noisy in the woods for them. I think moving around when they're wet also makes them colder so they move only as much as necessary.