I live in Michigan too, and also have a covered run. Despite the record mild winter we're having, we had a stretch of days in January in the single digits. On those days, I was very glad for the size of my coop, as I shut my 11 chickens inside, so that they could be sheltered from the wind.I am in Michigan and they will all have access to a large covered run along with a shed in their fenced in area. Thankfully, we also have many crows and have not had any problems with hawks this far.
Any wind at 5 degrees F is brutally hard on their feet, combs, and wattles. At the time, I had five 8 month old pullets, five mature hens, and a mature rooster. Eleven birds in about 60 square feet of coop. I was sorry it wasn't larger, but they did fine.
Roughly 5.5 sf per bird, about 38% more space than the "suggested minimum."
"Gee, I wish I'd made my coop/run smaller," is a phrase I never read here on BYC. More space is always helpful with chickens.