I've been told that chickens and rain do not mix and do not let them get wet. First, they can a chill and catch a cold and sometimes even die from it. Second, mine are show birds and getting wet from rain and being outside will surely make their feathers a mess. Third, been told chickens need shelter from the rain and especially do not need to be out in the weather when temps are freezing which could cause frostbite which is not a pretty thing and especially bad for their health.
Anyway, since I have show birds, I will do my best to keep them covered during the rain, but of course I can not be there for them every time it rains and they will get wet. The worst is not them getting wet, but the coop getting so smelly when it gets wet.
I do get my chickens wet when I give them a bath for a show and it takes 24 to 36 hours for their feathers to get fully dry. During the cooler months they will stay in a small coop in the house to get dry before a show.
Today, I had a sprinkler on the yard in front of the coops to help cool them down in the heat. The Ameraucana and Araucana chickens were out. Each time the sprinkler came their way, boy they all took off running to get away from the water. As soon as the sprinkler went by they ran back into the area that was wet on the ground. So you could say, mine do not like to get sprayed on but enjoy the wet ground.