My chickens love the run weather it's raining or not,but they do tend to go inside when it's heavy they love to play in the puddles that get made ,I sometimes dump bucket of water in there run in one spot so they can cool off and cuz they love it,but I use wood pune shavings in coop and in run its dirt so we put some fresh grass on top but they also have a corner were there is sand for them to lay in they live it