I was asked by my 16 y/o son
Q: I was asked recently (by my 16-year old son) about the responsibility for the snow on the roof of your car.
A: We often will see cars traveling around with a foot of snow on the roof. While there is no law that states you can't do this, it is probably not the best move. If this snow flies off the roof of your vehicle and lands on the windshield of another vehicle and that causes that driver to get into an accident, there is a pretty good chance that you could be held liable for causing that accident. In our legal system, your everyday actions are compared to those of "the reasonable person" standard. What would a reasonable person do in these circumstances? Our courts would consider if it was reasonably foreseeable that the snow might fly off your vehicle and cause another person to have an accident.
In the end, it takes a minute or two to wipe the snow off your vehicle. Don't take the chance--be safe and courteous to the other users of the road, which includes pedestrians. Its what our courts will likely expect from a reasonable person. As always, if you have a legal question, get good legal advice from a lawyer you can trust.