Okay, now let's talk weather. SF is in California, right? So all you need to pack are your bikinis, right? The tourist traps do big business selling cheesy sweatshirts that say "San Francisco" on them to people like you. We're in Northern California, which you hardly ever see on TV. If you're used to the east coast, you're expecting that if it's hot during the day, it'll be pretty warm all night long, but among other things the east coast has the old "Gulf Stream" keeping it percolating, and Northern California has a current coming down from Alaska. It may get hot during the day, it may even be really hot during the day in August (like say, 90 F), but it's entirely likely it could drop down to 50 F at night fall. You're not going to boil or freeze really, but working out a system of layers is a constant problem in this town. (And just to help confuse things a little more: it can be hot and sunny in one part of the city and cool and cloudy in another, so don't just look out the window and think you know what you need to wear.)

With some luck you'll have some night-time fog flowing into town. If you're psyched for some fog, I suggest a midnight expedition up into the hills somewhere. In general, the higher up, and/or the further west you go, the more likely you'll catch some serious fog (I understand that the neighborhood called "Sunset" on the west side of town was originally known as "Fog Bank" before the real estate agents got a hold of it).