Things About San Francisco Weather That May Surprise You

While San Francisco has a fairly mild climate compared to many other US cities, there are a few things you should know about the weather.

San Francisco in Summer

Mark Twain is attributed with saying, "The coldest winter I ever spend was a summer in San Francisco." Although the actual author of that quote is uncertain,  summers in San Francisco are generally cool and foggy and can be downright chilly, windy, and damp. While it probably won't rain, it's often drizzly and the fog can be heavy. Temperatures may get into the 70's but usually only for a short time. Don't expect to be comfortable with just shorts and a t-shirt and be sure to bring a jacket.

The Warmest Months in San Francisco

So if it's cold in summer, when is it warm and sunny? September and October are usually the warmest and sunniest months, when San Francisco gets its Indian summer. April and May can also be warm and sunny. It doesn't normally get hot in the city although spring and fall sometimes see temperatures in the 80's. You'll still need a sweater or jacket most evenings at least.

Sunny One Minute, Foggy the Next

San Francisco weather can be pretty unpredictable. Mornings may start out foggy and quickly change to sunny. In the afternoon the fog may roll in suddenly, especially near the ocean, cooling things off quickly. Even on a clear day, there can be fog at the Golden Gate Bridge. Or it may get windy in the afternoon. The best way to be prepared is to dress in layers.

Swimming in the Ocean, Sunbathing on the Beach

People often think of California beaches as sunny and warm with good places to swim in the ocean. While that's true in Southern California, it's a rare day that you'll see a beach full of sunbathers in San Francisco or along the coast north of the city. Only the hardiest people swim in the ocean and surfers usually wear a wet suit. If you plan to kayak or go boating in the bay, be sure to bring a jacket.

Warm Summer Spots Near San Francisco

South of San Francisco it's generally warmer than north of the city. In summer, the Napa and Sonoma Valleys can be sunny and hot. The farther inland you go, the warmer it will be (and colder in winter). For example, in the Napa Valley Calistoga is usually warmer than the town of Napa. Sacramento is hot in summer but in winter there's dense fog most days.