Yesterday, 28F:

+ +

Shimano MT21 + thin cycling socks + wool hiking socks = toasty warm feet

Today, 30F:

+

Shimano MT21 + wool hiking socks = cold feet

I wore the cycling socks yesterday as a fungus barrier, since none of my wool socks were clean. I'm shocked how much difference they made.

As to what constitutes "cold" I think it depends on the climate in which you live. I grew up in the hills of western Maryland and I had no problem going out in sub-zero temperatures. After 15 years living in the PNW, anything below 32 is quite cold. Your body adapts, I guess. Or maybe I'm just getting old.