How cold is too cold

[ckeene1990]

Here in Michigan it is going to get to -10 F at night. I know they say no heat, but this seems extreme, should I add heat for a few days during this time?

 

[StinkyAcres]

Most breeds will survive if they are healthy and their coop is adequate, but it's really up to you to decide whether you want to make them more comfortable or not by adding heat. Do you have a safe heater to place in the coop? Typical heat lamps are very dangerous and safe radiant panel heaters are expensive. Do you have large-combed birds that you want to protect from frostbite? Do you have silkies or frizzles?

 

[FrostRanger]

What breeds do you have and do you have especially young or especially old birds? As long as they have adequate draft free ventilation most birds are fine at those temps. Just make sure the water doesn't stay frozen (and keep it out of the coop as it adds humidity and humidity is the enemy here). Most importantly though observe your flock. If they are acting especially cold give them a little heat with a coop safe panel heater, otherwise let them be

 

[MROO]

Here in Michigan it is going to get to -10 F at night. I know they say no heat, but this seems extreme, should I add heat for a few days during this time?

How many birds do you have and how big is their coop? Chickens will huddle together for warmth.
It's important to remember that drafts and humidity are greater threats than cold temperatures. Make sure there are no drafts under their roost. Overhead ventilation is necessary, but lower vents/windows/leaks can be a real issue. If your waterer is inside and it has a heating element, that may keep temps a bit more stable, but you'll need to watch for frostbite because of the moisture.
If there's room in your coop and you're really concerned, you could put in a "huddle box" to limit the space their bodies have to heat. I've had a cardboard box buried in straw work for lean-to barn chickens. I propped it up on a straw bale so it wasn't on the ground and they took right to it.

 

[Murphyandme]

I am in northern nh and routinely go below 0. We have a small coop with 4 Rhode Island Reds. We keep a narrow vent open all the time. I close them in the coop at night and use a deep compost heat method. I replace the water in their run (covered with 5 mil plastic over the screening) every morning. We also have a temp gauge with a remote in the house. As long as they are out of any wind they seem fine. Artificial heat will cause humidity and that will be deadly for them. They seem fine and happy. They also have an opportunity to get outside in their pen during the day. Still getting eggs daily (although amount is reduced).