December 17th was the perfect day for a drive from my home near Whitehorse, Yukon, to Skagway, Alaska - very cold with high north winds at Skagway but clear all the way.

This is a shot of the temperature gauge in my car as I was about to turn onto the Alaska Highway at 9:24am. It only goes to -30°C (-22°F) - when that's what it reads the temperature could be anything lower than that. It was actually about -34° at…