Humans aren't that good at seeing in rain and fog either (which is why many people avoid driving or drive much more slowly in extreme rain and fog conditions),

Humans aren't that good at seeing in rain and fog either (which is why many people avoid driving or drive much more slowly in extreme rain and fog conditions), so saying robotic vehicles aren't good at driving in inclement weather conditions isn't very interesting. In addition to cameras, Waymo and Cruise vehicles have multiple lidar and radar units. These are all affected differently by inclement weather but in principle combining sensor data for perception gives the vehicle a lot more data to work off of than a human relying solely on vision. Driving in truly bad weather is still an open research problem, but it's also one that most of these companies haven't dedicated a lot of resources to, since they all have initial rollout plans in places that don't experience much extreme weather. But assuming these vehicles can drive well in good weather, I don't think it's a stretch to assume that progress will be made on driving in more extreme conditions once more resources are dedicated to it.