Water temperature in Clear Lake (CA) in September

Is it warm enough to swim in Clear Lake in September? Average water temperature in Clear Lake in September is 74.7°F and therefore suitable for comfortable swimming. The warmest water in Clear Lake in September is 80.1°F, and the coldest is 69.1°F. To find out the sea temperature today and in the coming days, go to Current sea temperature in Clear Lake

Changes water temperature in Clear Lake in September 2025, 2024

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

Average water temperature in Clear Lake in September over a decade

Chart comparing the height of waves in Clear Lake 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.

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

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

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Our report for Clear Lake 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.