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Water temperature in Lake Washington (WA) in September

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Is it warm enough to swim in Lake Washington in September? Average water temperature in Lake Washington in September is 63.1°F and therefore is not suitable for comfortable swimming. The warmest water in Lake Washington in September is 75.2°F, and the coldest is 55.4°F. To find out the water temperature today and in the coming days, go to Current water temperature in Lake Washington

Changes water temperature in Lake Washington in September 2025, 2024

To get an accurate forecast for the water temperature in Lake Washington for any chosen month, compare two years within a 10 year range using the chart below.

You can choose any other years:

Year 1:   Year 2:


Day 2025 2024
September 168°F66.2°F
September 268°F66.2°F
September 368°F68°F
September 466.2°F68°F
September 566.2°F69.8°F
September 666.2°F69.8°F
September 7 68°F
September 8 68°F
September 9 68°F
September 10 66.2°F
September 11 64.4°F
September 12 62.6°F
September 13 60.8°F
September 14 60.8°F
September 15 59°F
Day 2025 2024
September 16 59°F
September 17 59°F
September 18 59°F
September 19 59°F
September 20 59°F
September 21 59°F
September 22 60.8°F
September 23 60.8°F
September 24 60.8°F
September 25 60.8°F
September 26 60.8°F
September 27 60.8°F
September 28 59°F
September 29 57.2°F
September 30 55.4°F

Average water temperature in Lake Washington in September over a decade

20152016201720182019
65.5°F61.3°F62.8°F
20202021202220232024
64.8°F61.3°F65.1°F62.1°F62.6°F

Lake Washington 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

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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 Lake Washington 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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