I don't know if this is right or not, but my personal rule of thumb is full feathers, 6 weeks and 60 degrees. They have to look fully feathered, be at least 6 weeks old and the the night time low no less than 60 degrees. Right now, my oldest 2008 babies are 5 1/2 weeks old. It is only 37 degrees outside, but it is about 60 inside the coop during the day and probably 40 - 50 at night. There are 4 brooders in there with heat lamps so the temp is pretty warm in there. The 5 1/2 week olds are in a cage with the door open during the day. They have the run of the coop all day, and put themselves to bed under the lamp at night. They seem fine.
