I spent a few days in some C. walkeriana habitat in winter, I just didn't know it. This was in June, corresponding to December in the Northern Hemisphere. Days were in the 80-90 F / 26-32C range and nights in the 50s-60s F / 10-21C. Locals said it could get cooler but frost was something unheard of. I haven't been to all of its habitat, just this one part.
__________________ May the bridges I've burned light my way.