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September Weather in Mill Plain, United States

Last updated: June 24, 2025

In September, the average temperature in Mill Plain, United States hovers around 17°C (63°F), with a minimum of 6°C (42°F) and a maximum reaching 35°C (96°F). Expect about 111 mm (4.4 in) of precipitation spread over 9 days, contributing to an average humidity level of 71%.

September Temperature in Mill Plain

In September in Mill Plain, the average temperature is 17°C (63°F), with maximums reaching 35°C (96°F) and minimums dropping to as low as 6°C (42°F). This temperature range makes Mill Plain an ideal destination for travelers seeking mild weather and opportunities for various outdoor activities.

September Weather in Mill Plain: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Mill Plain, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Mill Plain, September typically has an average temperature of 17°C (63°F), with highs reaching up to 35°C (96°F) and lows dropping to around 6°C (42°F).
JanFebMarAprMayJunJulAugSepOctNovDec403945505762676963524540
Data source: Temperature data for Mill Plain 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 Mill Plain

In Mill Plain in September, the precipitation amount is 111 mm (4.4 in) over the course of 9 days.

September Precipitation Trends in Mill Plain

The chart displays monthly precipitation patterns in Mill Plain, 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 Mill Plain, September typically receives around 111 mm (4.4 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec24626018916686751013111199260273
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Mill Plain

In Mill Plain in September, humidity is 71%. With an average temperature of 17°C (63°F), this humidity feels like a warm embrace, making outdoor activities enjoyable yet a bit sticky, so travelers should stay hydrated and take breaks in the shade.

September Average Humidity in Mill Plain

This chart illustrates the average monthly humidity levels in Mill Plain, 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 Mill Plain is approximately 71%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec85%84%85%83%83%84%82%74%71%81%87%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Mill Plain

In Mill Plain 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 Mill Plain.

Maximum UV Index Levels in Mill Plain for September

The chart shows the monthly maximum UV Index (UVI) for Mill Plain 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 Mill Plain typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2356991087532
Data source: Mill Plain 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 Mill Plain Compares to Other Months

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

This table compares monthly weather conditions in Mill Plain, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather5°C (41°F)246 mm (9.7 inches)85%low
February Weather4°C (40°F)260 mm (10.2 inches)84%moderate
March Weather7°C (45°F)189 mm (7.4 inches)85%moderate
April Weather10°C (50°F)166 mm (6.5 inches)83%high
May Weather14°C (57°F)86 mm (3.4 inches)83%very high
June Weather17°C (63°F)75 mm (3.0 inches)83%very high
July Weather20°C (68°F)10 mm (0.4 inches)82%very high
August Weather20°C (69°F)13 mm (0.5 inches)74%very high
September Weather17°C (63°F)111 mm (4.4 inches)71%high
October Weather11°C (52°F)199 mm (7.8 inches)81%moderate
November Weather7°C (46°F)260 mm (10.2 inches)87%moderate
December Weather5°C (40°F)273 mm (10.7 inches)87%low

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