Last night was about 20. I closed their window last night, and left the light off. They seem to be thriving and doing very well. They were anxious to be outside today, and it was really cold out there. They happily ran out to chomp on a pumpkin slice from my jack o lantern I put in their run this morning. Lows are expected to be 17 by the end of the week. However difficult this is for me to do, I will leave off the lamp. They sleep on their roost all cuddled together. I think they must be about 10 weeks now. Lots of feathers and plenty of attitude in the coop. Thanks for all the advice. You people are very helpful.