When can chicks go outside in coop?

[Vamvakas]

I have chicks that are 2 weeks old now and I know it's abit early to put them outside now but I was wondering how old is the youngest age for them to live in the coop with out a lamp? I live in CT and it's usally late 50s-70s high at the moment and 40s-50s at night.

 

[azygous]

If you have power in the coop, you can move them in there any time, assuming there are no older chickens that would be a danger to them. Until chicks have their feathers, though, they simply cannot regulate body temperature. They need a heat source, even if the ambient temperature seems mild.

Around four weeks, they usually have enough feathers to manage without the lamp if the temperature at night is mild. If the night temp gets down in the 30's and 40's they'll need a lamp until six weeks at night.

If you have no power to the coop, best they stay in the brooder.

 

[Delta2 23]

I'd go for five weeks old, as your temps are sort of mid-range.
Ours were outside by four weeks but it's warmer here.