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Water temperature in Foster City (CA) in September

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Is it warm enough to swim in Foster City in September? Average water temperature in Foster City in September is 62.2°F and therefore is not suitable for comfortable swimming. The warmest sea in Foster City in September is 75°F, and the coldest is 55.6°F. To find out the sea temperature today and in the coming days, go to Current sea temperature in Foster City

Changes water temperature in Foster City in September 2025, 2024

To get an accurate forecast for the water temperature in Foster City for any chosen month, compare two years within a 10 year range using the chart below. In addition to the sea water temperature in Foster City, the selected years in the table also show the values of the maximum and minimum temperatures on each of the days of September.

You can choose any other years:

Year 1:   Year 2:


Day 2025 2024 Min Max
September 170.9°F70.3°F56.3°F72°F
September 271.4°F68.7°F56.5°F71.4°F
September 371.2°F69.3°F56.7°F71.4°F
September 471.4°F71.1°F56.7°F71.4°F
September 5 70.9°F56.7°F72.7°F
September 6 71.2°F56.8°F74.5°F
September 7 70.5°F56.7°F74.5°F
September 8 70.2°F56.5°F75°F
September 9 70.3°F55.9°F74.8°F
September 10 69.4°F55.8°F73°F
September 11 69.4°F55.6°F71.6°F
September 12 67.5°F55.8°F70.9°F
September 13 68.7°F55.9°F71.2°F
September 14 68.9°F56.3°F71.2°F
September 15 68.5°F56.1°F70.7°F
Day 2025 2024 Min Max
September 16 68.2°F56.5°F70°F
September 17 66°F56.8°F70.9°F
September 18 65.7°F57.2°F69.6°F
September 19 65.7°F57°F69.1°F
September 20 66.7°F56.7°F69.3°F
September 21 66.4°F56.7°F70.3°F
September 22 65.3°F56.1°F70.9°F
September 23 67.3°F56.3°F69.8°F
September 24 69.1°F56.5°F71.2°F
September 25 68.9°F56.5°F72°F
September 26 70°F56.1°F72.3°F
September 27 68.4°F55.8°F70.5°F
September 28 69.8°F55.9°F69.8°F
September 29 69.4°F56.3°F69.4°F
September 30 69.4°F56.3°F69.4°F
Foster City water temp chart in September

Average water temperature in Foster City in September over a decade

20152016201720182019
61.2°F58.5°F62.1°F64.4°F69.8°F
20202021202220232024
61.7°F69.8°F70.2°F69.3°F68.7°F

Foster City sea state in September

Chart comparing the height of waves in Foster City in September over the past years. The red line indicates the height of the waves when swimming in the sea is prohibited. To view the current sea conditions, click on the graph.

Waves height in Foster City in September

Foster City water temperature during other months:

You can also view information about water temperature for other months by clicking on the month button below

Where is the warm sea water in September?

Want to know where the water temperature in September is good for swimming? Select the continent of interest, the day of the month and the required water temperature

Region
Date (day and month)
Water temperature: min 60°F
 Average temperature  Maximum temperature

Best Beach Resorts in California in September

Places with the warmest average sea water temperature in California in September. In addition, the maximum and minimum water temperatures for that month, recorded over the last decade, are shown

AvrMinMax
San Diego69.1°F63.1°F75.6°F
Santa Monica68.4°F62.6°F73.4°F
La Jolla Cove70°F63.7°F76.1°F
Lake Tahoe64.9°F59°F70.5°F
Los Angeles68.2°F61.5°F74.3°F
Millbrae62.4°F55.6°F74.7°F
Mountain View61.9°F55.4°F74.3°F
Palo Alto61.9°F55.4°F74.3°F
San Leandro62.6°F55.6°F75.7°F
Oakland62.6°F55.8°F74.8°F

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[1] - The "Blue Flag" is awarded to beaches which fulfill a number of criteria, including: the quality of the bathing water, which must be in accordance with the relevant European Union Directive environmental education and information and beach area management and safety.

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Our report for Foster City is compiled using satellite data together with in-situ observations to get the most reliable daily data of sea surface temperatures, surf forecasts, current temperatures and weather forecasts.

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