If you have not had the pleasure, that is actually pretty cold. As in, you need to take precautions to keep all your bits you started with, as in you should avoid taking deep breaths, as in the kind of weather Jack London wrote about. Colder than Chicago at the moment.
So, when I read this story last week, about a couple of kids who decided it was the perfect time to take the bracing air, even though I am well aware that small children get up to all sorts of suboptimal things, I wondered, why weren’t they too cold to wander around? Perhaps they got too far before the chill really began to kick in? One kid apparently felt it enough to enter a house for shelter, but the other ended up with frozen fingers because she did not bother putting on the mittens she had in her pockets the whole time!
Low minus 30s in Rangely CO in the winter of 1980-1981. And I was sleeping in an unheated tarpaper shack in a sleeping bag. A damn good sleeping bag, rated to 40 below, silver goose down. But when a bag is rated to 40 below it doesn’t mean it will keep you toasty-warm and comfortable down to 40 below, it means it will keep you alive down to 40 below.
You have to look more closely at the actual ISO rating; it’s not just a single number. For example, a bag with an Extreme range of -28 C may only be comfortable down to -3 C, and be distinctly chilly with you curled up to conserve warmth by -9 C. Furthermore this is all on at least a foam mat, not, e.g., bare concrete, and you are assumed to be wearing a basic layer of clothes.
One time when I was in kindergarten, I walked home without my mittens on because I got a sugar cookie at school and I was afraid of crumbling it. It was probably only -10 Celsius or so, but my hands definitely hurt by the time I got home.
My guess is that the kids started off thinking that it was only a short walk, but then they got confused or panicked once they realized how cold it really was.