When do chicks come out of the brooder?

[photo chick]

I know it's been asked before but I just can't find the post. My chicks are 4 weeks old and in the brooder (aka bottom half of our dog kennel) in our bathroom. They are getting big. One of them loves to hop to the top and roost on the top of the brooder. We don't have a top on it because no one really seems interested in the "other side"!

We live in Vermont where it frosted last night (May 25th) and can vary between 50 degrees to 65 degrees during the day. Realistically when can we move them out of the house...even if it's for the day?

 

[PeeperKeeper]

I go by the weather and the environment. I live in northern KY and I have 2 week olds in a pet taxi outside tonight. And during the day, they go into a fenced pen area so the big girls don't eat them alive!
I'm still wondering how introducing new chicks into the chicken coop is going to go.