1 mile. That's enough.
We have sustained high winds this morning that have dropped the wind chill to -31. It's 5:25am and there's a full moon out, I had planned on running by moon light. Negative 31 degrees is cold. I'm thinking ski goggles and a baclava. The trick with the baclava is getting it to stick to your face. I find it's best to use one fresh from the oven. A balaclava would probably be smarter though.