Weather

SF, like London, is a city known for its fog. However, since we're right next to the Pacific Ocean, the city is not nearly as polluted. Most fog is known as the marine layer, a flat mass of cloud that is usually a few hundred feet above the ground. On some hills though, you can easily be up in the fog, which is actually a stratocumulus cloud. Overcast days with a thick marine layer are especially common in late spring and early summer, though it can occur all year.

As a result of all of this cloudiness and proximity to large bodies of water, the City stays moderately cool all year. Most days, high temperatures will be between 50°F (10°C) in winter and 75°F (24°C) in summer. Temperatures over 90°F (32°C) and below freezing (32°F, 0°C) are very rare, and will set records most days of the year. SF gets about 21 inches (54 cm) of rain annually, with the most rain falling November through March.

National Weather Service SF forecasts are some of the best forecasts. The San Francisco Weather Field Office (i.e. National Weather Service Office) is actually all the way down in Monterey.

Of course, we have a bunch of weird microclimates here — wunderground.com lets you pick between different weather sensors around the city.

There's much talk about how we've got different microclimates around the city. Here's a neat picture from Pam Peirce's Golden Gate Gardening: