I’ll start by saying this: if you’re running in the extreme cold make sure someone knows where you are, when you’re getting back, wear something obnoxiously visible, and stay close to a warm/dry location even if it means running smaller loops. A million freak things can happen that can stop you from being able to get home, and if you’re already damp with sweat a few miles can be a very dangerous distance. Don’t assume you’ll be making the best decisions when going hypothermic, and don’t rely on your phone with numb hands and batteries that don’t work well in extreme cold.
With that out the way: I ran down to -10F temps/-35F windchill last year, which I likely won’t do again. I never felt in serious danger with the right gear but it was really difficult to get a meaningful workout at that level. 0F/-10F windchill is reasonably comfortable if you’re smart and wearing clothing appropriate for the task. Notable that when it’s really cold I tend to only do aerobic/easy running - anything else is too tough on footing and easily leads to pulled/strained muscles for me.
Coming off the trot (where I crushed last year’s pace by 1:15/mi, nbd) for an easy 7 today. Christmas tree acquisition tonight, followed by drinks and decorations.
Tomorrow will be an easy few trail miles then the OSU/Mich game (go Bucks!). Helping a friend move to their new house in the afternoon.
Sunday long run (12ish?) then restocking the fridge/finishing cleaning the house from hosting Thanksgiving before it’s back to reality.