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.
Not sure what an autonomous car could have done in such a situation but anticipate that maybe we should preemptively pull over for a bit before it starts raining.
"I'm sorry, Dave, I can't do that. It's raining."
"Are you kidding me?! He's dying! Go! Now!"
"Did you try applying pressure to the wound?"
Let's hope that we never have cars that decide it's not safe for us to drive, "regardless of who's driving."
That's a common misconception, but I believe it was debunked by snopes.
From the positive side, they will collect and be able to evaluate a much /wider/ range of driving data from a far larger set. They are much more likely to run across 'better morons' both in operators of the Tesla and in operators of other cars.