There seems to be a cutoff point at about 40 degrees Farenheit. Below that, when I run on the treadmill at the gym, I seem to build up static electricity from the rubbing of my soles against the belt. Above that temperature I'm okay. Today was in the high 30's, and it was really dry in the gym.
This morning, I'd run about two miles on the treadmill when I reached for the towel hanging on the handrail. My hand brushed the rail and a powerful electric shock went through my body (no exaggeration, I think I spied an arc of lightning between my nipples), so strong that it went through my headphones to my iPod sitting in the drinkholder and seemingly shorted it out. After much panicked button mashing, I managed to reset my iPod and bring it back to life. That had never happened before.
After that I tried to ground myself every couple of steps, but that blew my mental concentration. Yet another reason I hate running on a treadmill.