I live in a wooded hilly frozen place, 3 months of summer and 9 months of poor sleddin as they say around here, (not that bad), but up until the end of May we can get freeze warnings, and I keep a woodfire going in the stove from October till May, most times. I've had chickens all this time. 3/4 an acre is what I have fenced off for them, and it could easily handle up to 50 for free range, but the most I have had is around 35. They need about 4 square ft for roosting, you would want them to cuddle and keep each other warm through the cold months, they do fine in the mid to low 30's, in their housing, you dont want drafts but you do want ventilation. On the coldest of the coldest nights, below zero days on end and nights dipping to 20 below, is a challenge. I have a big walk in cellar with cages for that purpose, but you dont want to warm them on normal winter nights, teens-30's, they do fine if they are a winter hardy breed. You can hang heater lamps, and they also make these mats in different sizes for seed starting, to put on under the shavings. When I get new chicks, I get them in May, keep them in a spot indoors with a heat lamp until they have all their feathers and can fly up to roost, and put them in the barn around the beginning of July, and they are good to go. Use a generous amount of straw and shavings on the floor, make sure they have light in the barn, (passive solar), and they will be fine. I get my chicks from two places, Murray Macmurray hatchery, and Meyers, and Hoovers, all ship good healthy chicks, MacMurrays sells good equipment. In the winter I put a kiddy pool in the barn with tube sand and wood ash mixed so they can dust themselves , as they will get lice through winter if they cannot dust themselves off. Sometimes you lose a few, but if you check on the flock once a day in the winter, and notice one or two all huddled and shivery and sleepy, they need to get warmed up, sometimes they are the ones on the end or the one that is unpopular and cannot get cozy enough, Make sure to get chicks that are labelled as winter hardy, and it should be fine.