Hi, first time poster here. I live in the Pacific NW and am brooding 4 chicks outside who are currently 4 weeks old and are super healthy. I have been using the "heating pad momma" method. It's October and starting to get to 40-50s during the day and freezing at night. They only get under "momma" at night and run around all day and are thriving. I've been reading other posts but not clear on the age I can stop offering heat at these temperatures. I've seen anywhere from 8 to 11 weeks and beyond so I'm a bit confused. This picture is about 2 weeks ago as I was building their brooder, but now they are fully feathered (except for my BR who still has a little fuzz on her head), I cover with a heavy tarp at night on rainy/windy days. For you PNW people, when do you stop offering heat under freezing temperatures?
Welcome to BYC! Glad you've joined us! Best advice I can give is to watch them and when they start choosing not to use the heat anymore, that is the best time to remove it. They will tell you when they're done with it.
I would turn the heat on any time it was below freezing until my chicks all had really good feathers, not the patchy dinosaur stage, so unti 8-10 weeks maybe. If it was really nasty out (for me it was April/May snow storms) I'd lock them in the coop for the day and would only let them in the run on warm dry days. I think the key is to try and keep them dry because they are still small and can't generate a lot of heat on their own.