What's Juyong like in December?

The temp in Juyongguan is usually 40F lower than downtown. More importantly, there is strong wind up there from northwest in winter time, which will make people feel much colder. If you'll go, wear your thickest and warmest clothes.
Actually, I don't think there is much too see in winter, except when it snows, and it will be amazing and grand then. But the thing is the stairs will be slippery if it snows and it's dangerous to climb the wall in that case.