Foster City Weather in September

In Foster City, September brings high daytime temperatures around 24°C (75°F), with nights cooling to 13°C (55°F). Minimal rainfall is to be expected.

Rainfall in Foster City in September

You can typically expect a single day of rain this month, averaging around 3.5 mm (0.1 in). Any rain that does arrive is likely to be light drizzle rather than a proper shower.

Temperature in Foster City in September

Weather in Foster City is at its excellent in September. Highs reach 24°C (75°F), while nights settle around 13°C (55°F). Overall, the month follows a fairly predictable daily temperature pattern. Nights drop to around 13°C (55°F), which is noticeably cooler than the daytime. A light jacket for the evening is a sensible addition, and the cool nights tend to make sleeping comfortable. On average, it is the month with the highest temperature of the year.

Sunshine in Foster City in September

With approximately 270 hours of sunshine, the days are filled with clear skies. It makes it a perfect month for being outside.

Wind Speed in Foster City in September

Average wind conditions reach 5 m/s (10 knots) in September. This creates lively weather with fresh winds that make small trees sway noticeably. Remember this is an average: some days are less windy while others have particularly active windy conditions.

Average water temperature in September

The water is 14°C (57°F) this month — cool enough to feel refreshing on a warm day, but cold enough that most people won't stay in for long without a wetsuit.

If your ideal day consists of dry skies and pleasant temperatures, May, June, July, August, September and October typically offer the best circumstances for Foster City.

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• January
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• May
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• October
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• December

For a detailed overview over the year and the best time to visit the United States of America, check out our Foster City's climate page.

Foster City Temperature in September

Min Temperature 13°C (55°F)  

Max Temperature 24°C (75°F)  

Water Temperature 14°C (57°F) *  

Chance of Rain 3%  

Precipitation 3.5 mm (0.1 in)  

Rainy days a single day  

Humidity 73% *  

Windspeed 5 m/s (10 knots) *  

Sunshine 270 hours *  

Percentage Sunshine 73% *  

* Data from: San Francisco, the United States of America (11 KM, 7 Miles).

What to Wear in Foster City in September

For Foster City in September, you'll want flexible clothing. It's wise to pack cotton shirts, comfortable shorts, and a pair of jeans for cooler evenings. A light sweater or jacket is useful for air-conditioned spaces (like buses) or unexpected cool moments. Almost no rain is expected, so no need to bring rain gear. Expect water temperatures of around 14°C (57°F), which is definitely too cold for comfortable swimming. Your luggage space is better used for other items. And with plenty of sunshine hours, don’t forget sunglasses, sunscreen, and maybe a sun hat.

What To Do in Foster City in September

We rated the following activities from 1 (least suitable) to 10 (best) to do.

Swimming

10/10

Cycling

10/10

Walking

10/10

Barbeque

9/10

Camping

10/10

Outdoor sports

10/10

Select a Month

Check the conditions for any month of the year.

• January
• February
• March
• April

• May
• June
• July
• August

• September
• October
• November
• December

For a detailed overview over the year and the best time to visit the United States of America, check out our Foster City's climate page.

More climate data for Foster City

Temperature Rainfall Sunshine Humidity Wind Speed Water Temp

See the full Foster City climate overview or explore weather in the United States of America.