I’m roughly in your zone, the border of 6 and 7 depending on which map you look at. I’ve put chicks straight from the incubator or post office into my 3’ x 6’ brooder in my totally detached unheated coop. Sometimes that is in February with overnight (and sometimes daytime) temperatures well below freezing. On rare occasions it is in July or August when the temperatures are hot. As long as you can provide heat you can handle it.
One problem with brooding them outside, either in a totally detached building like I do or in an attached garage, is that the temperature is not constant. It keeps going up and down, sometimes by a lot. There is no way you can keep that brooder at a constant temperature. But that is so easy to handle it’s ridiculous. Make your brooder large enough so you can heat one area warm enough in the coldest temperatures and the far end is cool enough in the warmest conditions. I find the chicks straight from the incubator are really good at managing their own temperatures as long as they have options. I’ve had extremely young chicks in there when the far end had ice or frost on it, but the end they were in was toasty. I use a heat lamp but others use other methods. There is no one right way to do it where other ways are wrong. We all do things differently. You just need to find a way to keep one end of the brooder warm.
I’ve put five week old chicks raised in my brooder into my unheated grow-out coop when the overnight lows were in the mid 20’s Fahrenheit. No heat provided. Those chicks were used to playing all over my brooder so they were used to the cold, they were acclimated. My grow-out coop has good breeze protection and great ventilation up high.
People are always happy to tell you why you can’t do something or what the best way or time is. I often find the best time to do something is when you can.
Good luck!
