Winter.
I'm letting my beard grow. It began between Christmas and New Year's. I'm working as a contractor at Microsoft. I asked another bearded fellow as we walked to the elevators whether he thought having a beard provided extra warmth in the winter. He emphatically answered yes. These Microsoft folks are generally sharp and knowledgeable, but I was skeptical and asked how he knew it. "Because it's uncomfortably warm in the summer," he replied.
My first 30 years were spent in Southern California, so I need to remind myself to be careful in winter. A mantra I'm repeating silently with each four footsteps on cold days is WATCH OUT FOR ICE. WATCH OUT FOR ICE. WATCH OUT FOR ICE...