One of my favorite activities while walking the Great Wall was to stop up, and photograph the things I walked past. You can go here to see photos I took in the beginning of my trip.
The winter of 2009-2010 is the coldest I will hopefully ever experience. I spent a lot of it outside, sleeping in a tent at night, and hiking the Great Wall during the day hours. I lay down a rule that if the temperature was lower than -25C / -13 F I would try and find a place inside. Here are some photos from that winter.
I also experienced up to +45C temperatures and high humidity while hiking in Hebei close to Beijing. During the final stages of my walk, I covered the equivalent of 32 marathons in 41 days. That was in the Liaoning Province on my way to Datong on the North-Korean border.