Just to avoid confusion, Muir Woods is north of SF in Marin County, as Joe Offer said,m not south. Big Basin is the redwood park that is near Santa Cruz -- that's near where I live, and I would be happy to play tour guide for that if you wish (or for Monterey, Santa Cruz, or Point Lobos). Not that I'm an expert guide...

I would like to note that although we think of California as hot in August, it's usually quite a tolerable dry heat, and in many areas (though perhaps not in our Central Valley) it can be relied on to cool off at night.

Claire