San Francisco snow, also know as broken glass on Bay Area streets. Too commonly Bay Area residents fall victim to "bippers" or car break in professionals.
Advice to those unaware of the bip culture in the Bay: be careful of where you park your vehicle, install tinted windows, park in well lit areas, leave a index card visible that says NOTHING is in this car, PLEASE don't break my WINDOW! But, MOST importantly NEVER LEAVE ANYTHING in your CAR.