-33 degrees.. How cold is too cold?

[chalidobrenz]

I know people have asked this before, but the temperatures of concern were only in the mid 20s to low 30s. Tonight it is supposed to dip down to -33 degrees F, and I'm worried about my birds! That seems unreasonably cold. My coup is insulated and draft free, and they have a water heater to keep it from freezing, but even a heat lamp doesn't keep it above 10 degrees in there right now. I have one hen who is conveniently molting at the coldest part of winter, and is nearly naked necked and has no feathers on her head. :/ I know chickens are hardy birds, but it is SO cold! Suggestions?

 

[Messipaw]

Look here
https://www.backyardchickens.com/t/944110/7f-and-all-is-well#post_14537910https://www.backyardchickens.com/t/944110/7f-and-all-is-well#post_14537910