"So," a friend of mine asked, "what do the chickens do when it rains like this?"
Just about everybody has asked, so finally I will post a picture with proof:
They just stand out in the rain. Sometimes they look indignant that somebody is sprinkling water on them, but mostly they do their normal stuff, or as normal as it can be. Only during the worst downpours have I ever seen them take refuge in their room, although it is open and available to them all day.
When the sun comes out, they fluff up and dry out. If it doesn't come out, they seem to just stay out in the rain all day until sunset, when they get up on their perch and preen in the nice dry chicken room.