I had my current two chicks at 5 weeks and the experienced breeder I got them from said it was fine to put them out in a small sheltered run on short grass during the day and bring them in at night. He said don't let them get wet as they're not fully feathered yet. So I have them in a small coop with a wire arch top, and I've put a sheet of plastic over the top, retained by elastic ropes, to give shelter from wind and rain. They get plenty of air as the coop has uncovered mesh front and back, and also the plastic doesn't completely cover the arch, just the top and the side where the wind is coming from that day. I place the coop somewhere where shade is also available at all times during the day, and I move it every day so they always get clean grass in the morning, and hose down the previous day's spot to keep the grass growing. They're now 9 weeks and growing really well.