Could you maybe provide a covered area for them to give them some space during the day, just in case? That's a lot of snow, so I'm not sure what options you have.
Maybe try it out before winter really let's you have it. Lock them in there for a day or two. If it's bad, then build a fence...
First, let me say that I am sorry that folks lost their homes in the fire. I live in fire country, too, and the past few years have been horrendous.
As far as your chickens go, I think the biggest problem in winter is humidity. If your coops are well ventilated and the birds are protected...