I was born there under a heavy rain. it lasted about three minutes. My uncle who still lives in Poway has fucking sandbags at the ready is it rains for more than half a day. Then again, he has them at the ready for when Obama comes for his guns, so that isn't saying much to his intelligence despite the climate.
Rain looks way, way less severe on camera. When they film rain in movies, they're actually dumping about ten times the water you see on screen on the actors.
Having lived in a lot of different places, some of them with actual weather, I've always been amused by how much SoCal folk freak out when it rains.
That said, the last couple rounds of rain here were as bad as anything I've seen. Unable to see the lines on the road at a dead stop in daylight kind of bad.