You may consider taking them in for the night. I know the next few days are predicted to be cold/rainy/ with possibility of some

snow. That is for my area. You are further north so chances for snow/colder are very much a possibility. They are still not very feathered out.
Them being back in loft during the day is a good choice, so mom n pop can feed them.
When I had lil ones early in the year, and it was cold, I placed a heatlamp under the area where nest bowl was . The warmth made the floor of the loft somewhat warmer. I did with what I had. If I had an Electric Adjustable Heating Pad, I would have used it instead.
My heatlamp was outside of the loft enclosure , but loft was inside garage. It did not shine light into loft.