Yes, it is very hard on their systems to go from quite cold to warm and back again. Possumqueen had a lot of problems with sick birds when she did that. Do you have an area inside that is fairly cold, like in the garage? Say just above freezing, or less than 45 degrees? I am very concerned when I hear about people bringing the chickens inside for the night--I hope they are not bringing them into a 60 degree house and then expecting to put them back outside in 20 degrees after a few days! What temperature range are you talking about (inside and outside)?