I have 4 chicks and a duckling that are all about 3-ish weeks. I live in Boise and the temps during the day now are getting up to anywhere from 54-74. They have a good number of feathers in already and although the duck is later in getting her feathers than the chicks she is larger, fatter and covered in a cozy layer of white fluff. As soon as the temp reaches above 50 in the morning I take them out of the brooder (in the garage) and put them out either in the run or I let them run in the yard if I am planning to be out with them. They stay out most of the day now and they don't even need the lamp anymore. I do put them back in the brooder at night still. I am waiting at least another week before putting them in the coop because it still gets chilly at night and I would rather not wire the lamp out there. What I hear from most people is that the sooner you expose them to lower temps, the hardier they become and the less suceptible they are to cold later on. Certainly I'm not going to make them freeze but they have seemed perfectly comfortable so far and I would rather not have to ever put the lamp out in the coop.