The sunroof seal ( not on the moving panel ) is not meant to be a watertight seal. A certain amount of water will get past this seal, but the roof assembly has drains built into it. Behind the "A" and "C" pillar trim you'll find rubber hoses that get the water from the sunroof frame to the ground. The exit points are beneath the car, just behind the front wheels, and just forward of the rear wheels. As far as using the sunroof in cold weather? In my opinion the sunroof motor is stronger than the brackets and sliding jaws that guide the roof panel during operation. If something is binding it will eventually break. It's sort of like trying to use the wipers to clear a foot of snow off the windshield.