What's all over the car?

We had some snow/rain yesterday and noticed white stuff all over the windshield when we went out last night. At first my husband thought it was soap that didn't rinse off well after the last car wash.  Then he noticed that all the cars in the neighborhood have the same stuff.  The word on the street is that it's either from a dust storm that got swept up into the snow clouds on their way here, or a lake effect from the storm system moving over the Great Salt Lake, or dust from the desert.  Strange.