Those are average temperatures, not necessarily the extremes you will see over the next few weeks. You have to remain a little bit flexible in how you approach it.
My brooder is in the coop from Day 1. A couple of weeks ago I put some chicks in there and within a couple of days the outside temperature was single digits Fahrenheit. But the chicks were not outside they were in a brooder with one end pretty toasty. The far end of my 3’ x 6’ brooder even had some ice in it so it was pretty cold but the chicks did not go to the far end. Instead they stayed in the warm end. Smart 2 day old chicks.
If you can safely heat one area in that coop you could move them out now. I’d leave them locked in the coop portion and not give them access to the run section for another two or three weeks, just so they don’t get stuck out here somehow.
A broody hen does not heat up the entire universe for her babies. She provides a warm spot for them to go to when they need to warm up. There is no reason to keep the entire brooder one perfect temperature. Just keep one spot warm enough and let the rest cool off as it will. You’ll find that as long as the temperatures aren’t real extreme they will soon be playing all over that brooder anyway, just going to the warm end when they get chilly. They do tend to sleep in the warmer area.
When you put a bunch of people in a room with an average temperature, some are too warm, some are too cool, and some are just right. Why? Because are people are different. Chicks are different too. Some prefer it cooler, some prefer it warmer, and some don’t seem to care that much. As long as you heat one end and let he rest cool down, they can make themselves comfortable.
I am convinced that they feather out faster and get acclimated to cooler temperatures if they are exposed to cooler temperatures. You accomplish this by heating one end of the brooder and let the rest cool down, if you can. That can be more difficult in your house where you keep the thermostat set at a fairly warm temperature.
Now, some of my urban legends. I’ve had 5 week old chicks raised in my brooder go through nights in the mid 40’s Fahrenheit in a grow-out coop that had no heat, good draft protection, and good ventilation up high. I’ve had chicks raised that way in the same grow-out coop go through nights in the mid 20’s before they were 6 weeks old.
I’ve seen a broody take her chicks to the roosts at 2 weeks. A couple of them did not make it all the way but spent the night on top of the end of a 2x4 brace on the coop wall. It was summer and pretty warm. They were fine. In summer, I’ve had a broody totally wean her chicks at three weeks and leave them on their own in the flock. They did fine.
One really hot summer, I turned the daytime heat off in that brooder at Day 2 and the nighttime heat off after day 5. By the way they were actin the chicks told me they did not need the heat and they really didn’t.
Each situation is unique. That’s what I mean by being flexible. I try to pay attention to the chicks and let them tell me what they need. I understand you probably don’t have a lot of confidence in speaking “Chick Language” just yet. That will come with experience, if you are willing to learn.
Good luck with it. It’s a good journey.
