60 overnight,at 4-7 weeks? They'll be just fine. As long as they have dry bedding,no major drafts,& other buddies to snuggle with, No worries.
I'm in Kansas,my newborns go out to the coop once they are dry in the bator, under a heat lamp,dry bedding. They do just fine w/ no heat in daytime in 60+ temps once they have started to feather out a bit,as long as there's no storms,rain,lots of wind. Breed does make a difference, however. I wouldn't leave tiny bantams out, but I have no problems w/ my healthy,stout kids such as Buff Orps,RIR, & EEs ,etc.,both from the hatchery & hatched from my gals.
As long as as it is a warm,sunny day,I slowly wean mine off the heat lamp, the more REAL sunlight the better. AT 2 weeks or so, if temps are sunny & in the 70's & no wind I will let mine out on grass in the sun,they grow SO much faster. Key is to watch them,if they are running about exploring,they are fine,huddling together or piling up,too cold.
I have seen broodies take chicks out in 30 degree weather,& they seem just fine,just run to Mama when cold. I personally believe too much coddling weakens the stock.