I got a temperature gauge in the garage. Once it goes below 50 degrees I'm going to run a small space heater in there around the clock. My garage is attached and below, so it doesn't get too cold, and I figure its easier than dragging all my stuff upstairs. I have a fairly decent amount of stuff. Also, I would have to drag the Karcher upstairs, as if any left over water inside it freezes its ruined.
Waxes stay upstairs in a case all year around.
As for detailing in the cold, it won't stop me, I will adapt. Dress warm and I just picked up some rubber up to the elbow plumbers gloves at Harbor Freight that will keep my hands and arms clean and dry. I've washed my car when the water started to freeze on the panels. This year I'll switch the hose to hot water through the washing machine water feed.
I'll probably do a lot at the local DIY Spray and Pray Coin Op Car Wash. They have a bay where the one side of the door goes down like a garage door. When its cold you can stay in there all day without being bothered. I'll use their pressure sprayer and their killer air dryer, which is like ten Master Blasters at once.
A lot of times I will pressure wash with their water. Then I'll clean the wheels with a Montana Boars Hair Wheel Beush and a Daytona Wheel Brush for the barrels. After that, I'll rinse again and finish with their "spotless water". Then I'll dry with their air dryer and then do a waterless or rinse-less wash, depending how dirty vehicle is. Nobody has ever bothered me and you get 13 minutes of pressure wash or hot air drying for 5 bucks.