I am in the same boat. SW OH on May 12 who would expect night temps in the 30s? 4 1/2 week old orps did fine last night…second day in the coop…a huge rain and thunderstorm the first night with standing water in their run. Surprised none wanted to come out? So last night I closed the doors and put a 75 watt work light in there. I don't know about physiological stress but all 6 seem happy. They are almost all feathered so I'm sure that helps. I really appreciate the advice on this website. And a tolerant/helpful husband!