That’s a real common question on this forum and you’ve provided about enough information to give a good answer. Chicks can go outside when they have feathered out, but you factor in weather a bit. Also, the coop they are going to should have pretty good draft protection. I think yours are good to go, but I’ll give some more info.
When chicks are feathered out depends on a few things. If they are started on a fairly high protein chick Starter in the range of 20% to 24% protein, they will feather out faster than if they are kept on a low protein feed from day 1, such as a 16% protein Grower. If they are on a Starter they should pretty much be feathered out at 4 weeks, maybe at most 5 weeks. Then you can switch to a Grower. They’ve already feathered out.
Something else that makes a difference is if they are exposed to colder temperatures, they can better handle colder temperatures. It’s like people that live in a tropical climate flying to somewhere with snow on the ground. No matter how they dress, they are cold. Chicks raised where they are exposed to colder temperatures feather out faster and are better acclimated.
At that age it is highly likely they will spend the night on the floor, not roosting. I’ve had a few start roosting that young but most wait until they are 10 to 12 weeks old. If you have some bedding in the floor for them to snuggle in and drafts are not blowing on them, they can stay pretty warm. They can snuggle with each other too and provide warmth, but even if it is warm they’ll probably sleep together just because they enjoy the company.
I raise my chicks in a permanent brooder in the coop. I only heat one end of that and let the rest cool off as it will. This winter I had chicks just a few days old in that brooder when the overnight low was 4 F above zero. The end they were on was toasty but the far end had frost the next morning. They were fine. That was an extreme but at three weeks they now spend a lot of time in the far parts of that brooder with the daytime temperatures in the upper 40’s or 50’s. They are getting acclimated.
A couple of years ago I moved some chicks from that heated brooder to an unheated grow-out coop when they were 5 weeks old. The overnight lows were in the mid 40’s. Before they hit 6 weeks they went through a night with the overnight low in the mid 20’s. There were about 20 of them, no heat, good draft protection, and were on wire with no bedding so they could not snuggle down into anything. But they were acclimated and had been fed a fairly high (20%) protein feed for probably the whole time. They were all fine.
I don’t know what your coop looks like for draft protection but at that age yours are probably ready for the move.
