Ok, at below zero, I have sometimes popped on a heat lamp to get the coop up to 0 degrees F. I am trying to wean myself off of this, and go cold turkey (or NOT cold chicken ). I believe my chickens will survive just fine in 30 below zero, as long as they are out of the wind and snow. And are dry. What is the coldest air temps your chickens have been at? And does it make a difference whether it is daytime or at night on the roost?