Weather in San Mateo County, United States in September

So you're interested in going to San Mateo County, United States in September

September is a slightly cold and very dry time for sunbathing in San Mateo County. September is a good month for swimming in San Mateo County with warm sea temperatures. Consider visiting San Mateo County in the months of June, July, August, September, for the best beach weather. Also consider one of our other suggestions for September.

Temperature in San Mateo County in September

The average maximum temperature in San Mateo County in September is 18°. The average maximum temperature is 17° in the previous month and 18° in the next month.

The average temperature in San Mateo County in September is 14°. The average temperature ranges is 14° in the previous month and 14° in the next month.

The average minimum temperature in San Mateo County in September is 11°. The minimum temperature is 12° in the previous month and 10° in the next month.

Sunshine in San Mateo County in September

The average day light hours per day in San Mateo County in September are 12.4 and there are 9.2 hours of sunshine per day on average during September making it a sunny month with few clouds.

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 24.1° which is warm and pleasant for relaxing and swimming for long periods.

Rainfall in San Mateo County in September

The average total rainfall in San Mateo County in September is 0.5cm 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° which is comfortable for everyone. The dew point is 14° in the previous month and 13° 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 22kmh. The average maximum wind speed is 20kmh in the previous month and 24kmh in the next month.

The average wind speed in San Mateo County in September is typically 9kmh. The average wind speed is 9kmh in the previous month and 8kmh 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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