I've seen wind and rain push the turkeys out into the fields more. I think the increased noise and movement in the woods negates their keen senses.
God made the toms to strut in sunlight and show off all their colors, so it stands to reason that they'll strut less on rainy days (instinctual)
As long as it's not a downpour, rainy days can be great....if you can find a field they're going into.
And like dukkillr said, they'll usually stay on the roost alot longer in the morning.