I have outdoor chicks. They were out there at 3 days old and with lows in the upper teens. Aside from needing to watch that their water was close enough to the heat that it didn't freeze, I didn't do anything different. Shelter from the elements and a spot to warm up is all that is needed. So, they have a small coop with a heating pad hen in it but at 2.5-3.5 weeks of age, they spend most of their daytime out in the run whether it's 30 degrees or 60. They make more frequent trips to warm up if it's cold and windy but they don't choose to stay indoors. They really aren't as fragile as humans tend to think.