If you get a min/max thermometer and pop it into the coop, you should be able to find out how low it gets in there.I've been a bit concerned about the water freezing. If it has, it's been a thin skin gone by mid morning I would have thought. Last year the bowl of water in the coop froze but I think that was around -6C overnight and it didn't get above freezing for a couple of days.
