I put my chicks outside by themselves for the first time last night. I don't know what temp it dropped to, but I'm guessing around 35- 40 or so. I left a heat lamp out there with them, covered the little pen with plywood and a tarp and crossed my worried fingers that they would not be overly upset at being left out. When I checked them this morning, they were all huddled under the lamp, but seemed no worse for the wear. In fact, they seemed happier than they are in the house. They weren't even peeping, even after I peeked in to check on them. I am not going to integrate mine in with the other hens, I want to keep the pens separate, so I don't have to worry about that!