Despite being not too far from the coldest (record: Snag YT, -81F,
3/2/1947) part of the Great White North of Leftpondia (Kanuckistan, Silvan), it's never too cold to be in the shop. Note the numerous discussions on the merits of various means of heating the shop we Leftpondians constantly engage in.So the answer is: the shop & tools are cold when you start, but gradually warm up. 7-8C and above is quite confortable. But then, as we like to say, it's a dry cold. Remember, it's not the cold, it's the humidity.
The coldest I've ever seen the shop was -20C when it was -47C outside.
You need (1) insulated coveralls (the LOML got me new ones for Christmas) (2) a tuque and (3) gloves (either wool & thinsulate with open fingers and a mitten cover or thin fleece (e.g ). The coveralls and tuque keep your body core and head warm and make it easier for your body to send warm blood out to your fingers. You should remove the gloves when working close to a rapidly whirling sharp object, but bandsaws are OK.
I find it OK to work with power tools down to about -5C, but usually it's not for very long as the shop is warming up. After an hour or two, I ditch the coveralls.