I also have put out my month and a half old chicks in the grow out pen which is right next to the run for the flock. It has been in the 30s at night and as high as 60 during the day. Our weather has been rainy, today we had a May snow storm. I am from Wisconsin and i guess our chicks/chickens must be hardier as this is what I do every year and have never had an issue with temperatures. I have a dog igloo in the grow up pen where they only stay for 2 weeks to a month, it is kept clean and has bedding inside. No rain or snow penetrates the inside of the igloo. This works for me and i never have any problems integrating the young with the old, or problems with them using the main coop or roosts. Until it does warm up every night i give the chicks additional food to help keep them a bit warmer during the night.
I have babies (chicks less than 3 weeks old) that i keep inside the greenhouse inside of a brooder box, which maintains heat well but I do use a heat lamp at night. I also have bigger chicks (4-6 weeks) inside the barn in their own pen who i do not provide additional heat for at night, just bedding.
Our temperatures most likely make some chicken owners nervous but I think it's the same way the temperatures in Arizona or Australia make me uneasy.
