I have 23 Isa Browns, hatched 10/26, that were in a brooder in my unheated mudroom until the day after Thanksgiving. They are now are outside in an insulated coop with a nice thick layer of straw on the floor. They have a Sweeter Heater radiant heater that, honestly, they don't even go under anymore. They sleep at the opposite end of the coop! The front coop door is open during the day, even the cold crummy ones and they have the choice to go out if they want or stay in. It's almost a given that they will go out.
I had a hen hatch a chick in September and it was the first time I got to witness how a mama hen takes care of her chick. She took her outside on day two!!! Seemed crazy to me, but I learned that baby chicks are a bit sturdier than we give them credit for. Like others said, as long as they have a dry place out of the wind and weather with a heat source until they are feathered (around 6-8 weeks) they should be fine. And from what I've seen, mine much prefer to be outside.