If the sky gets that greenish look, you know it is going to be bad and to get to shelter. Scary part is when you do not get the color warning. (Either it is dark or pops up quickly)
I don't know if tornadoes ever "grow" in California. But from what people say who have experienced them I'd put that at the top of my list too. Mother Nature can be very vicious and deadly. Thank you for your reply m2c and Happy Thursday to thee and thine! :)