With temps THAT cold, for THAT long, I would definitely find a way to expand your coop, as I worry that you would have serious behavior issues due to confinement/overcrowding. If your chickens are young, they MAY do okay with another coop added, sharing a run...but I think you'd have to keep them shut inside for a week or two to retrain them. You might even temporarily divide the run so that they HAVE to go back to the new coop. Is there a way of expanding the coop?? I know it's harder to modify and insulated coop, but we're doing so with ours...knocking out most of a wall and expanding another 4 feet for our expanding flock. With winters like yours, I would want much more than the 4 sq. ft. minimum that's recommended for areas that get winters.
I would definitely wrap your run in tarps so that there'd at least be windblocks to encourage them to get outdoors. There's also those clear roofing panels - I screw those onto my smaller run to block wind, because they still let the sun in - but they're costly. Or there's always downsizing by a few chickens...many old time chicken owners would keep a larger flock during the summer, but downsize come winter time.
I would definitely wrap your run in tarps so that there'd at least be windblocks to encourage them to get outdoors. There's also those clear roofing panels - I screw those onto my smaller run to block wind, because they still let the sun in - but they're costly. Or there's always downsizing by a few chickens...many old time chicken owners would keep a larger flock during the summer, but downsize come winter time.