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What is the Weather in San Francisco in September?

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This post is a summary of the weather in San Francisco, with tips on what to wear and things to do.  If you are traveling to San Francisco in September, congratulations!  You could not have picked a better month to visit. Many people expect that summertime would have the best weather in the area, but actually, September has the best weather during the entire year. It's very sunny and quite warm (at least for San Francisco standards) for most of the month.


AVERAGE TEMPERATURES

The average high temperature during the day is 70 degrees F (21 C), with peak temperatures of the month often reaching up into the mid-80s (30 C). The average lows will be around 55 F (13 C), with nighttime temperatures not generally getting anywhere below 52 F (11 C).

 

Average Temperatures September San Francisco

 

There are still some factors to consider while you're visiting, and we'll go over all that in this post. But in general, you should expect that the weather on your trip is going to be about the best all year long in San Francisco. So read on to hear how to prepare for your trip!

 


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AVERAGE DAYS OF SUN AND RAIN

A common question asked by newbies to the city is - do I Need an Umbrella in San Francisco in September? Almost certainly not. The average rainfall for the month is only 0.21 inches (5.3 mm). That's for an entire month!

San Francisco weather averages 1.7 days of "rain" during the month. But as the locals can tell you, a "rainy" day here is not like in many other places around the world. The sky drops a little bit of mist for 15-20 minutes, and then the skies clear up for the rest of the day.

 

Sunshine in San Francisco in September

 


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WHAT TO WEAR IN SEPTEMBER IN SAN FRANCISCO

As we mentioned earlier, you will often see very warm temperatures in September. Especially if you're going to be walking around sunny areas you should be prepared for the heat.

The Best Plan: Layers!

As we mentioned in our post about the weather in August, it can get a little cold in the mornings and evenings in our city. So we suggest bringing a light jacket on your travels.

When the sun goes down in San Francisco, temperatures will begin dropping. San Francisco does not have much humidity, so the heat really disappears when the sun is not shining. Also, if you are going to be walking around the waterfront area, or if the day happens to be a bit chilly or windy, you will have to be prepared.

The key here is to dress in layers. If you walk around San Francisco at any time of year, you will see people wearing shorts or long pants (depending on the day), a t-shirt, and either wearing or carrying a light jacket. When the sun is shining and it's warm, the jacket will come of. When the sun goes down or it's a bit windy, the jacket comes back on. Very easy!

In San Francisco in September, the average wind speed is only about 11 mph (18 kph), with maximum breezes increasing to about 20 mph (32 kph). So remember to bring that jacket!


THINGS TO DO IN SEPTEMBER

There are more things to do in September than we can list here, so be sure to read our full post on what to do and see this month, as well as our master post for any time of the year. Below is our top choices.

And if you are planning on visiting many of San Francisco's top attractions, then you should consider a tourist discount pass as you could save up to 50% of retail ticket prices to tours, attractions, and restaurants.

 

  1. Sausalito Art Festival
  2. Fringe Theatre
  3. Peak 2 Peak
  4. California Rum Festival
  5. Opera in the Park
  6. Comedy Day
  7. Folsom Street Fair
  8. Oktoberfest by the Bay
  9. Free National Park Day
  10. Union Square Live

Find out more and read our full post on what to do and see this month,


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Written by Fred Pickhardt

Ocean Weather Services

 

About The Author

Fred Pickhardt

Fred is a marine meteorologist and sailed briefly with American Export Lines in the Far East trade. He has extensive experience in weather analysis, weather forecasting, and forensic weather event reconstructions. Fred founded Ocean Weather Services and currently provides forensic marine weather reports to the maritime industry.
Updated: September 27th, 2021
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