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September Weather in Chehalis, United States

Last updated: June 24, 2025

In Chehalis, United States, the average temperature in September is a comfortable 16°C (61°F). However, temperatures can range from a chilly 4°C (40°F) to a warm 32°C (91°F). During this month, you can expect about 88 mm (3.5 in) of precipitation spread over 10 days, with an average humidity of 74%.

September Temperature in Chehalis

In September in Chehalis, the average temperature is 16°C (61°F), with maximums reaching 32°C (91°F) and minimums dropping as low as 4°C (40°F). This wide temperature range makes Chehalis an ideal destination for travelers looking to experience a variety of climates.

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

The chart illustrates September temperature patterns in Chehalis, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Chehalis, September typically has an average temperature of 16°C (61°F), with highs reaching up to 32°C (91°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec414044495560646560504540
Data source: Temperature data for Chehalis 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 Chehalis

In Chehalis in September, the precipitation amount is 88 mm (3.5 in) spread over a duration of 10 days.

September Precipitation Trends in Chehalis

The chart displays monthly precipitation patterns in Chehalis, 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 Chehalis, September typically receives around 88 mm (3.5 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec1871691371197154121588132181198
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Chehalis

In Chehalis in September humidity is 74%. With an average temperature of 16°C (61°F), this humidity feels like a damp blanket wrapping around you, making traveling quite uncomfortable as the air feels thick and muggy, potentially leading to fatigue and a longing for a cool breeze.

September Average Humidity in Chehalis

This chart illustrates the average monthly humidity levels in Chehalis, 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 Chehalis is approximately 74%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%85%83%84%84%82%73%74%83%86%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Chehalis

In Chehalis 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 Chehalis.

Maximum UV Index Levels in Chehalis for September

The chart shows the monthly maximum UV Index (UVI) for Chehalis 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 Chehalis typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec235699987532
Data source: Chehalis 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 Chehalis Compares to Other Months

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

This table compares monthly weather conditions in Chehalis, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather5°C (41°F)186 mm (7.3 inches)86%low
February Weather4°C (40°F)169 mm (6.7 inches)84%moderate
March Weather7°C (45°F)137 mm (5.4 inches)85%moderate
April Weather10°C (49°F)119 mm (4.7 inches)83%high
May Weather13°C (56°F)71 mm (2.8 inches)84%very high
June Weather16°C (60°F)54 mm (2.1 inches)84%very high
July Weather18°C (65°F)12 mm (0.5 inches)82%very high
August Weather19°C (66°F)15 mm (0.6 inches)73%very high
September Weather16°C (61°F)88 mm (3.5 inches)74%high
October Weather10°C (51°F)132 mm (5.2 inches)83%moderate
November Weather7°C (45°F)181 mm (7.1 inches)86%moderate
December Weather5°C (40°F)198 mm (7.8 inches)87%low

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