Indeed, it's more about shelter than temperature.Cold begins at -15 °C.
The issue is not the nominal temperature, per se, but the wind. Without the wind, I don't mind -50 °C; but the wind can make even -20 °C a real bitch.
I smoked a cigar in -30 once and it wasn't the worst thing ever, you just need to be prepared.
My two most valuable pieces of kit (the boots were acquired locally at the time):
MammothWorkwear.com - The worldwide workwear company
mammothworkwear.com
Ice Trooper
Our most popular men's hat! Velcro closure secures flaps up over the head or fasten under chin for a warmer fit. Made from genuine sheepskin. Care guide here. Adult Sizes. Made in Canada by Egli's Product Code: 100073 Children's sizes also availableIce Trooper with Mask also available...
eglifarm.com