...for vision heavy rain isn't terribly different from a blizzard...I would say that heavy rain is incredibly different from a blizzard. Snow has a much greater horizontal-to-vertical velocity, reflects more light, and flutters around. Rain mostly moves in straight lines, even in high wind. Not to mention traction is completely different on water vs. slush vs. snow vs. ice, as well as with good snow/rain tires vs. worn all-season tires.
I'm sure Tesla knows all this, but just in case you haven't driven in a blizzard before, you will need to drive very, very differently from driving in heavy rain.