Weather in San Mateo County, United States in September

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Visiting San Mateo County, United States in September

September is one of the best months to visit San Mateo County for the best beach weather. It has the most sunshine and best sunbathing and swimming conditions of the year.

September has average maximum temperatures of 18°C (64°F) which is not that warm but sunbathing may be possible on some clear days. The sunshine percentage is 74% making it sunny and pleasant most of the time. The hours of sunshine per day are 9.2hrs making the days long and bright. September has total rainfall of 0.5cm (0.2inches) making it extremely dry with very few light showers and most days are rain free. There are just 3.1 days with some rainfall so you can still enjoy the beach on the majority of rain free clear days and rainy days are few and far between. Sea temperatures are a cool 20°C (68°F). September is a slightly chilly month for swimming in San Mateo County.

Also consider visiting San Mateo County in one of the other best months of June, July, August, for the best beach weather.

Also consider one of our other suggestions for September.

Can you sunbathe in San Mateo County in September?

No, September is not a good time for sunbathing in San Mateo County.

September has average maximum temperatures of 18°C (64°F) which is not that warm but sunbathing may be possible on some clear days. The sunshine percentage is 74% making it sunny and pleasant most of the time. The hours of sunshine per day are 9.2hrs making the days long and bright. September has total rainfall of 0.5cm (0.2inches) making it extremely dry with very few light showers and most days are rain free. There are just 3.1 days with some rainfall so you can still enjoy the beach on the majority of rain free clear days and rainy days are few and far between.

More about September temperature and sunshine.

Can you swim in San Mateo County in September?

Yes, September is a a slightly chilly month for swimming in San Mateo County with cool sea temperatures 20°C (68°F).

More about September sea temperatures.

Is September a good time to holiday in San Mateo County?

Yes, September is a slightly cool time for a holiday in San Mateo County.

September has average maximum temperatures of 18°C (64°F) which is not that warm but sunbathing may be possible on some clear days. The sunshine percentage is 74% making it sunny and pleasant most of the time. The hours of sunshine per day are 9.2hrs making the days long and bright. September has total rainfall of 0.5cm (0.2inches) making it extremely dry with very few light showers and most days are rain free. There are just 3.1 days with some rainfall so you can still enjoy the beach on the majority of rain free clear days and rainy days are few and far between. Sea temperatures are a cool 20°C (68°F). September is a slightly chilly month for swimming in San Mateo County.

More about the September temperatures and sunshine.

Is San Mateo County warm in September?

No, San Mateo County is not that warm but sunbathing may be possible on some clear days in September.

The average maximum temperature in San Mateo County in September is 18°C (64°F). The average maximum temperature is 17°C (62°) in the previous month and 18°C (65°F) in the next month.

The average temperature in San Mateo County in September is 14°C (58°F). The average temperature is 14°C (58°F) in the previous month and 14°C (56°F) in the next month.

More info about the September temperatures and sunshine.

How sunny is San Mateo County in September?

The average day light hours per day in San Mateo County in September are 12.4. The sunshine percentage is 74% making it sunny and pleasant most of the time. The hours of sunshine per day are 9.2hrs making the days long and bright.

More about September sunshine.

Temperature in San Mateo County in September

The average maximum temperature in San Mateo County in September is 18°C (64°F). The average maximum temperature is 17°C (62°F) in the previous month and 18°C (65°F) in the next month.

The average temperature in San Mateo County in September is 14°C (58°F). The average temperature is 14°C (58°F) in the previous month and 14°C (56°F) in the next month.

The average minimum temperature in San Mateo County in September is 11°C (52°F). The minimum temperature is 12°C (54°F) in the previous month and 10°C (49°F) in the next month.

Sunshine in San Mateo County in September

During September the average day light hours are 12.4 per day in San Mateo County. The sunshine percentage is 74% making it sunny and pleasant most of the time. The hours of sunshine per day are 9.2hrs making the days long and bright.

The ultraviolet index in San Mateo County in September is typically 7.7 during September. An ultraviolet index reading of 8 to 10 indicates a very high risk of harm from unprotected sun exposure. Unprotected skin risks burning in less than 15 minutes. Take extra precautions because unprotected skin and eyes will be damaged and can burn quickly. Tanning will be safest before 10am and after 4pm but only with a good application of sun screen. For those with sensitive skin stay in the shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days. Watch out for relections from water that may increase ultraviolet exposure.

Sea Temperature in San Mateo County in September

The average sea water temperature in San Mateo County in September is 20°C (68°F) which is comfortable for swimming though some may prefer warmer water.

Rainfall in San Mateo County in September

The average total rainfall in San Mateo County in September is 0.5cm (0.2inches) and on average there are 3.1 rainy days in September making it a very dry time to visit the beach.

Humidity in San Mateo County in September

The maximum dew point (an indicator of humidity) in San Mateo County in September is 14°C (58°F) which is comfortable for everyone. The dew point is 14°C (57°F) in the previous month and 13°C (13°F) in the next month.

The average maximum relative humidity in San Mateo County in September is typically 98.6%. The maximum relative humidity is 99% in the previous month and 97% in the next month.

The average relative humidity in San Mateo County in September is typically 90.4%. The average relative humidity is 92.3% in the previous month and 83.8% in the next month.

Wind Speed in San Mateo County in September

The average maximum wind speed in San Mateo County in September is typically 22KM/H (13MPH). The average maximum wind speed is 20KM/H (12MPH) in the previous month and 24KM/H (15MPH) in the next month.

The average wind speed in San Mateo County in September is typically 9KM/H (6MPH). The average wind speed is 9KM/H (5MPH) in the previous month and 8KM/H (5MPH) in the next month.

The average wind direction in San Mateo County in September is from the West-Northwest.

Monthly Averages

Suggested Beaches in September

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Beaches recommended for you today, this weekend, in the next 2 weeks or in any month of the year.

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Need Inspiration?

Beaches recommended for you today, this weekend, in the next 2 weeks or in any month of the year.