I just put some 3 week old bobs out but it is 80* at night here till the last coupla days heat index tomorrow is supposed to be 100* for me it depends on what the temps are and time of year the last ones I put out I waited 4-5 weeks it was cooler outside
My bobs will go out in about 3 weeks, when there 4 weeks old, but I have the opposite problem as you, here its way too hot, during the day it may get up to 115, right now its in the 100 and 105, so I dont know if my little bobs will be able to endure this kind of heat, the adults do but the babies I dont know how hardy they are.
I also have 4 other quails and a chuckar who are 5 weeks old and there still in the brooder, I put them outside in the day but at night I put them inside with a lamp.
You start temp. at 100 and lower it by 5* a week or until its 70* outside which it may differ. can be up to 6 weeks. The way I do it is check under their wings and see if they are fully feathered or if you can still see skin. You'll of course want them to be fully feathered before turning them loose without any heat. Like BOTH said above their in differant parts of the country it can be 3 weeks or until the temp. is the same for a low as it is in the brooder.