There has been very little spraying in California over the past few months.
Then, about ten days ago, there were a few big events going on simultaniously in San Francisco area: the fleet week including the air show with Blue Angels, the Mill Valley Film Festival, Bluegrass festival, and so on.
These shows attracted tens of thousands people from all over the world and the US.
In the early morning hours of the bussiest days, such as Saturday, Oct.9 2010, one could see the clear blue sky above San Francisco and surrounding area completely covered with chemtrails. The spraying actually started the night before.