what does the temp need to be before it's safe for chicks outside?

[lulumammato2]

I've got 6 BR about 5 weeks old 1 Cochin,one EE both about 4 weeks old i,ve been putting them outside in their coop with their lamp during the day but i'm afraid it might still be getting a little too cold at night what does the overnight temp need to be?

 

[Olive Hill]

With a lamp it can be below zero and they would be fine.

At any rate all should be feathered out within a couple of weeks and you will be able to put them out then without heat regardless of temps.