That yellow dust is pine pollen. Each spring pine trees release yellow pollen sometimes so thick it looks like a cloud. It is harmless unless you have an adverse reaction to pollen. However it makes water look polluted and forget spring cleaning for a few weeks. I recommend closing doors and windows on windy days plus dust and vacuum often to keep your living space cleaner. Rain helps knock it down, but then California does not get much in late June. Then in a few weeks when pollen has settled, deep clean your home. We may get some cottonwood seeds (looks like snow) floating around in July, but the pollen is done for the year. Linda Morris, California Naturalist
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