Apparently just subzero is not enough. Some significant amount of extended cold is required.

I know I get confused and paranoid about these critters. For example, is an itchy spot a mosquito bite, a bedbug bite, or just dry skin? Are the insides of my eyeball itching because - why? Would I really get symmetrical itching on the backs of my knees from bedbugs (I think that was dry skin in a dry climate). How do you know it's bedbugs or not with random itching?

I was creeped out several months ago when I saw a mattress leaning against the wall of my closest coffeeshop, with the sign "Caution Bedbugs!". No one has thrown away that mattress yet, although it was moved behind a dumpster. Just writing this post is making my ear canals itch (very unlikely to be bedbugs ).