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September Weather in Sammamish, United States

Last updated: June 24, 2025

In Sammamish, United States, the average temperature in September hovers around 15°C (60°F). Expect lows of 5°C (41°F) and highs reaching up to 31°C (89°F). During this month, precipitation can amount to 124 mm (4.9 in) across approximately 12 days, with an average humidity of 62%.

September Temperature in Sammamish

In September in Sammamish, the average temperature is 15°C (60°F). The maximum can reach 31°C (89°F), and the minimum can be as low as 5°C (41°F). This makes it a great time to visit Sammamish, as travelers can enjoy pleasant weather with a nice range of temperatures for various activities.

September Weather in Sammamish: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Sammamish, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Sammamish, September typically has an average temperature of 15°C (60°F), with highs reaching up to 31°C (89°F) and lows dropping to around 5°C (41°F).
JanFebMarAprMayJunJulAugSepOctNovDec413944495560646559504540
Data source: Temperature data for Sammamish generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Sammamish

In Sammamish in September, the total precipitation amount is 124 mm (4.9 in) over a span of 12 days.

September Precipitation Trends in Sammamish

The chart displays monthly precipitation patterns in Sammamish, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Sammamish, September typically receives around 124 mm (4.9 inches) of precipitation spread over approximately 12 days.
JanFebMarAprMayJunJulAugSepOctNovDec21524216715494883427124220239248
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Sammamish

In Sammamish in September, humidity is 62%. With an average temperature of 15°C (60°F), this humidity feels like a warm embrace, making it a bit muggy for traveling, yet pleasantly refreshing for leisurely strolls and outdoor exploration.

September Average Humidity in Sammamish

This chart illustrates the average monthly humidity levels in Sammamish, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Sammamish is approximately 62%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%86%87%84%81%82%79%63%62%83%89%88%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Sammamish

In Sammamish in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Sammamish.

Maximum UV Index Levels in Sammamish for September

The chart shows the monthly maximum UV Index (UVI) for Sammamish in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Sammamish typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec235689987522
Data source: Sammamish September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in Sammamish Compares to Other Months

Weather in Sammamish varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Sammamish, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Sammamish, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather5°C (41°F)215 mm (8.5 inches)86%low
February Weather4°C (39°F)242 mm (9.5 inches)86%moderate
March Weather7°C (44°F)167 mm (6.6 inches)87%moderate
April Weather9°C (49°F)154 mm (6.1 inches)84%high
May Weather13°C (56°F)94 mm (3.7 inches)81%very high
June Weather16°C (60°F)88 mm (3.5 inches)82%very high
July Weather18°C (65°F)33 mm (1.3 inches)79%very high
August Weather18°C (65°F)27 mm (1.0 inches)63%very high
September Weather15°C (60°F)124 mm (4.9 inches)62%high
October Weather10°C (50°F)220 mm (8.7 inches)83%moderate
November Weather7°C (45°F)238 mm (9.4 inches)89%low
December Weather4°C (40°F)248 mm (9.8 inches)88%low

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