In SF you have fog haters and fog lovers.  I'm a lover because it looks cool and is great air conditioning.  Granted, I live near it more so than in it which is good because it's one of those things that's usually best experienced from afar.

Everyone's seen Mt. Sutro look like this:

But not everyone has seen the reverse view.  When the Pacific fog rolls over the hill, this is what the view of SF looks like from inside that evanescing blanket of former seawater:

Here's the nighttime view.  It's really cool to hang out and watch various parts of the skyline appear and disappear as the random patches of fog blow eastward.  Market Street is the bright line, and you can see a car's headlights and taillights on a nearby hairpin turn:

Full res pics can be found here.