This is going to be the real test for Waymo. From anecdotal experience, Austin has more inclement weather, and its road infrastructure is lacking in some parts of town.
However, in my experience, Austin roads are uniquely bad in one respect: surprisingly often, lane markings are so faded you cannot tell where your lane is. It's even worse when it rains.
Sometimes it is so bad that I know neither I nor anyone else can tell where their lane is, and I make a conscious decision to drive differently to compensate for that. I don't know if autonomous vehicles are going to deal with that very well.
SF doesn’t get snow or hurricanes
It is not at all unusual for people to get killed this way. They think their car can make it across, and they're wrong.
It's a problem in many parts of Texas because severe thunderstorms happen frequently and some of them bring heavy rain. But in Austin, it's especially bad because Austin is hilly, which makes flash floods worse.
Houston, by comparison, might as well be a river for how often it floods and how widespread flooding tends to be there.