20 degrees below zero. When I was a kid, I used to live on a snowmobile in the Buffalo area winters. I lived on the highest hill right off the lake. Ten feet of snow was not uncommon. My dad ran the blizzard of '77 snowmobile rescue operations. He even took a pregnant lady on a snowmobile to the hospital for the delivery. I also learned that eye temperature is the first thing that would make you sleepy. When I would finally stop in to go to the bathroom and get a bite to eat, I would be quickly overwhelmed with the desire to sleep.

Sledding probably, but I rarely checked temperatures as a kid, just bundled up and went for it. Most interesting story though:

Hunting/camping trip with a buddy; late December; nighttime low was projected to be mid 30s. Turned out to be wrong. And to make matters worse I was in a hammock that I had not yet fully winterized. To make matters even worse, we'd bedded down at the southern end of a lake, and as we were eating supper the wind shifted to come from almost due-North, and never really stopped again for the entire time we were there. Also it had rained before we arrived, so starting a fire took a good bit of effort.

So I in my hammock, and he in his tent, had just settled down before our fuel was all spent. We slept for a bit, even the coyotes went still, but then we awoke to a wicked wind-chill. It was my buddy's first trip, and he didn't know, so he borrowed my mylar and I layered on more clothes. We both lay back down, and my hammock did sway, the passed by slowly, in a cold, windy haze. Before dawn I awoke and mustered my nerve, to leave my cocoon for the frost-covered earth. I looked for my friend, but in its place stood a tomb, of icy crystal and diamond hewn. I called and I cried but my friend barely stirred, like a bear in the winter he was dead to the world. I left him behind and I went for a piss, for the Sleeping Beauty inside I'd not kiss. Our breakfast I cooked, my friend fin'lly awoke, but dreams of venison went up in smoke. The sky was alight, our schedule was far in areas, and for the next two days we saw nary a deer.

Seriously though, at one point we found the caretakers station and he told us the temperature hit 20 degrees that night and that while he didn't have a way to measure, the wind-chill was a good bit lower than that. Less than pleasant when we'd prepped for closer to 40 with negligible wind. When the rain came back on the third day we decided to pack out our gear and then hike to another spot we'd scouted out and see if we could find anything. So with all our gear on our backs, and complaining loudly of the litter other people had left we set out for the truck. And about 50 yards from our camp we bumbled upon the single biggest buck in the area, the one everyone wanted to take. Walked right up behind him no more than 25' away drinking at the water's edge. We saw each other at about the same moment, he snorted and bounded out to about a 10 yard shot and stopped to look back. We all stood frozen, staring for I really don't know how long. I had my bow strung and my quiver was still accessible in spite of all the gear I was carrying, and I was trying to decide if that little movement would scare him off. But he made up his mind before me and ran off before I could even twitch my hand.

All in all, it was a cold, wet, miserable experience. I had a blast and somehow my friend let me talk him into going back. One of my best friends now and now we take all of the guys back to that spot. A win all around as far as I'm concerned.

I used to ride a motorcycle daily to work. Where I live it doesnt snow. One January my 1 hour ride to work it was 37 degrees out, and it was fucking frozen.

Not sure the exact temp, but the coldest for me was doing DensGlass on the outside of a hospital here in Michigan. The coffee in my insulated cup was frozen solid by the time I got off the lift for first break. One of the worst jobs I've ever done.

This was 10+ years ago. It doesn't get that cold in Michigan anymore

Went camping with a couple buddies in February in Alaska - It was about 20 below zero. Just one of those "Let's see if we can do it." kinds of things.

Spent an hour or so walking outside in -54°c with the wind chill in Winnipeg.

Used to be -30° c regularly where I grew up, while we played hockey in our yards.

Not a whole day, impossible, but in minus sixty degrees windchill trying to start an Indian car. Everyone else already went to shelter. When my feet started to go numb i went into the house, too. Have had people freeze to death just a few streets away. It gets real.

Bakken oil fields of North Dakota it was usually around ten below f. Pretty much start work predawn and don't wrap up operations till dark. That was a brutal Christmas season. Worst day was twenty below zero f. and nothing would start. Supervisor never arrived due to frostbite trying to get his vehicle to the job and another vehicle blew radiator as it had not been winterized. I was only employee who had winterized my radiator . BTW, frostbite toes was a daily hazard even with special boots. For that you take a few minutes in the warmup shack until you can feel your toes again.

19° US Air Force Classified nuclear weapons stuff.