Like, my own behavior is now changed. If I am in an area under that kind of heavy rain potential, I am going to treat that like a blizzard and do what I can to make sure me and my loved ones are not in cars as it unfolds. I think people hear "rain" and just go about their business. Need to find a way to make the difference apparent. "Turn around don't drown" pre-supposes people in cars. "Do NOT leave your homes and if you do be aware of possibility of rapidly rising water" maybe? Something like that?
I would say it's moot as an infrequent occurrence but...these are not infrequent occurrences anymore...