Well, if you can take their heater out there..I wouldn't wait a moment longer.
If the 'chick coop' is adjacent to the main coop, even better.
Check this out:
https://www.backyardchickens.com/articles/integrating-new-birds-at-4-weeks-old.72603/
Or if you don't want their heater out there you can close off brooder room from rest of house, close house heat off in there and open a window to acclimate to the cooler ambient temps....and consider a huddle box:
Make them a 'huddle box', put it in the brooder after turning off the heat(you might have to 'persuade' them to use it) then move it out to the coop with them.
Cardboard box with a bottom a little bigger than what they need to cuddle next to each other without piling and tall enough for them to stand in.
Cut an opening on one side a couple inches from bottom and big enough for 2-3 of them to go thru at once.
Fill the bottom with some pine shavings an inch or so deep.
This will give them a cozy place to sleep/rest, block any drafts and help hold their body heat in.
If the 'chick coop' is adjacent to the main coop, even better.
Check this out:
https://www.backyardchickens.com/articles/integrating-new-birds-at-4-weeks-old.72603/
Or if you don't want their heater out there you can close off brooder room from rest of house, close house heat off in there and open a window to acclimate to the cooler ambient temps....and consider a huddle box:
Make them a 'huddle box', put it in the brooder after turning off the heat(you might have to 'persuade' them to use it) then move it out to the coop with them.
Cardboard box with a bottom a little bigger than what they need to cuddle next to each other without piling and tall enough for them to stand in.
Cut an opening on one side a couple inches from bottom and big enough for 2-3 of them to go thru at once.
Fill the bottom with some pine shavings an inch or so deep.
This will give them a cozy place to sleep/rest, block any drafts and help hold their body heat in.