parts of mexico. now barrelling north towards the u.s. in cabo san lucas, heavy rain pounding the tourist hot spot. and tonight, in southern california, this dire warning. make no mistake, this is a very very dangerous and significant storm. reporter: residents from san diego to palm springs, bracing for disaster filling sandbags to protect against potentially catastrophic floods i m pretty worried, yeah, yeah reporter: just a few inches of rain in desert areas like palm springs can be catastrophic because of the sun baked, dry hard soil and sand which doesn t easily absorb water, sending flood waters rushing on to roadways and into neighborhoods. but it s not just rain officials say the storm could cause life-threatening rip currents, deadly mud slides, and even tornadoes