-40 C is the same as -40F so without running the calculations, et's as cold as the op says.0C is 32F, so math wise 32 less 35 is actually -3F, right? Or no?
I'd worry that there are only two birds to huddle next to each other. My cold blasts are nothing like the OP, but you could wrap the roosting area in tarps to completely block the wind--I did that once and it helped. Sometimes in extreme storms the wind comes from an unexpected direction.
they aren't coming off the roost. I hand fed them some tuna this morning to get them hydrated and they ate some scratch and to since they aren't coming off for water or food. thankfully going to warm up significantly over the next few hours but boy, I feel bad for them! I also noticed each one (there's just two) has a small frozen patch on their back feathers. Could this be from snuggling into each other and their breath freezing onto their feathers? I just noticed it and thought it was strange. there are no condensation signs in the coop, it's well ventilated and dry. Any ideas?