If it is a light rain, they will go ahead and pitch down. Generally if it is hard they may stay on the roost till the rain stops. What I noticed in Nebraska this season is that after a night of rain, the birds pitched to the west side of the draws or where they would get 1st sun (to dry them out). On clear, warmmornings generally pitching to east side and heading to the bottoms(where the timber is)during the day to escape the hot sun.