but WHEN can I move them outside?

[AngeliqueR]

In California I was told to wait until nights are over 60 degrees. I think the primary difference may be the weather-hardening in your coop: in New England I assume your coop is ready for a real winter with snow and freezing temps whereas my southern California coop only has to be rain-proof, so chicken people here may be a bit more cautious about cold temps. I like the 45 degree advice though because my 3-week olds seem totally ready and we're well above that...

 

[Blooie]

My coop, here in Northern Wyoming, is neither insulated or heated in any way. There's an electrical outlet out there, and a light, but that's just for me on those days when nighttime comes at 4:00 and I still have chores to do. My brooder is out in the run. I don't do anything for winter protection other than put a stock tank heater in the waterer (that's what the outlet is for) and put some plastic up around part of the run to cut the worst of the wind and keep the snow off them.

I don't use a heat lamp out there, either. I use a heating pad and straw. It was in the 20s the day this was made.

 

[Ol Grey Mare]

My coop, here in Northern Wyoming, is neither insulated or heated in any way. There's an electrical outlet out there, and a light, but that's just for me on those days when nighttime comes at 4:00 and I still have chores to do. My brooder is out in the run. I don't do anything for winter protection other than put a stock tank heater in the waterer (that's what the outlet is for) and put some plastic up around part of the run to cut the worst of the wind and keep the snow off them.

I don't use a heat lamp out there, either. I use a heating pad and straw. It was in the 20s the day this was made.

Yep - even in the mountains of Idaho my coop was neither insulated nor heated -- I made no alterations for winter. It was not wired, nor is my coop now, so the only difference in winter is packing water out 2-3 times a day.

 

[Egghead_Jr]

No insulation, no heat, temps -30F in winter and no problems.

Like I'd stated earlier, our 10 day forecast has a lowest low of 39F. That's nothing for a group of 3 week old birds weened from heat lamp overnight in a shelter blocking wind. That's my 3 climate zones North of OP's location. Really nothing to worry about at all. Good to go.

I may have to wait until near 5 weeks to put out first batch of chicks and that's not due to weather rather the overload of broody birds we suddenly have so had to move them to the grow out coop and pen so I could take back the layer coops nests and get eggs. I may try and put the first group in with the broody birds. Not for them to brood but there is enough space for to roost and they've the pen to play and eat in all day. They might stay clear of one another and live in harmony. I'll have to watch them first day is all to see if the broody get all defensive.