I think they're just west-coast-centric and consider any precipitation at all to be substantial since we get almost nothing here on the west coast all winter. You at least get sprinkles, or fog, or mist, or something. When raindrops actually fall here in the winter, they leave huge splotches on cars. I'm not sure if it's because they pick up so much dust on the way down and are essentially mud drops, or if it's because they displace the two months of dust accumulated on the cars. Probably a bit of both, but I think most of it is due to accumulated dust not on the cars, but in the air. I haven't seen rain, real rain, since at least August. Even the last typhoon didn't bring us anything.