Just depends what you're doing. I'd rather it be at least -10 if I have strenuous activities planned -20 is better. At -40 it starts becoming difficult to use your fingers for any amount of time, they get pretty stiff and numb once they leave a mitt even with the thin wool liner gloves. But humidity has a lot to do with it, I'd take -40° at 100 miles inland over 0 on the ocean any day.

The coldest I’ve ever seen was November 14, 1976. Atigan pass on the Alaskan pipeline. The weather station at dead horse told us over the PA system that it was 83 below zero with a 30+knot wind. They said that their instrumentation was pegged out and that the windchill was somewhere below -120. My father and I were half of the team that made one of the tie ends. If I remember correctly, a welder by the name of Red Brown was the welder on the other side of the pipe. every time I look at a propane bottle, it reminds me of that day because we helpers had to hold a flame of a weed burner directly on the bottle of propane that we had hooked up to the pipe heater to generate enough gas to produce a flame. Again, if my memory serves me correctly, we had to use a 140°F temp lack stick before the welders could strike an arc without fracturing the pipe.

More to the OP‘s point -20 with proper clothing is doable all day long but what we were doing, and when we were doing it, humidity played very little part. The conditions were literally deadly.

Anything under 40 is miserable

Yep

Like said above, it’s all relative. 33 and raining sideways or -40 dry and calm. Easier to dress for the latter. Metabolizing calories creates heat. Insulation keeps it in

I'm a steadfast believer that 33-36° and raining is the most miserable situation a man can encounter for weather. I managed to deal with it for the first 30 years of my life in SE, I'm a little further north these days but this year hasn't been much different than home around here lol

Last winter, I pulled my wet hands out of the water to do something and plugged them in right quick. Freezer thought I was nutz when I told him I was warming them up…lol. I’d pull em out and quickly dry them off on my shirt under my parka and back into the gloves.
I’ve never brought chesties for ice beaver, I feel around the best I can with a stick. But getting in would certainly confirm the best spots.

The stripping of cloths and Dylatov Pass incedent comes to mind. I wonder what Tatiana thinks about this?
https://en.wikipedia.org/wiki/Dyatlov_Pass_incident
There’s all kinds of shows on this event.

That was the old timers way,we feel for the sides of the run with a stick not the entrance itself.
A lot of runs are wide enough for 2 or 3 traps side by side for multiple catches.

The water doesn't warm one up as much as chiseling the ice lol.

Great pic Steve.

I doubt many Alaskans trap beaver at 40 below.

There is actually a surprising amount of trappers that do. I, however, am not one of them!

I cringe if I have many sets out and it drops to that. Happens tho

That how you got your name 3 fingers?lol.
Froze em right off?

Was low on bait anyway

31-33° is the worst. When coupled with 90-100RH you will never not feel cold.

I will second that. Top it off with a nice stiff breeze blowing that rain in your face and it is about as miserable as you can get. That being said, I've not seen more than -30 Fahrenheit by the thermometer (a couple of times I'm sure it was colder than that, but I was camped out in the mountains or once the high desert, and didnt have a thermometer) so I can't speak to the truly cold that some of these guys can. But I can say that I'd much rather be out in -20 and calm than 35 above and rainy and windy. -20 and windy is pretty miserable also, though.

Another result of extreme cold is metal becomes brittle, and when struck while under tension, it will break instead of bend. At the Skagwon river, crossing the pipe, just barely banged against the side of a side, boom and a piece about the size of a lawnmower blade, but more pointy came out of the side of the boom so fast it actually sounded like a ricochet. thank goodness no one was standing in its path.