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September Weather in Rainier, United States

Last updated: June 24, 2025

In Rainier, United States, the average temperature in September hovers around 16°C (62°F). Expect temperatures to range from a cool 5°C (42°F) to a warm 34°C (93°F). During this month, precipitation averages 79 mm (3.1 in) over about 9 days, contributing to an average humidity of 71%. Stay prepared for a mix of weather as you explore this vibrant destination!

September Temperature in Rainier

In September in Rainier, the average temperature is 16°C (62°F), with maximums reaching up to 34°C (93°F) and minimums dipping as low as 5°C (42°F). This pleasant temperature range makes it an ideal time for outdoor activities and exploration in Rainier.

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

The chart illustrates September temperature patterns in Rainier, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Rainier, September typically has an average temperature of 16°C (62°F), with highs reaching up to 34°C (93°F) and lows dropping to around 5°C (42°F).
JanFebMarAprMayJunJulAugSepOctNovDec414045505661656661514540
Data source: Temperature data for Rainier 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 Rainier

In Rainier in September, the precipitation amount is 79 mm (3.1 in) spread over 9 days.

September Precipitation Trends in Rainier

The chart displays monthly precipitation patterns in Rainier, 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 Rainier, September typically receives around 79 mm (3.1 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec183166145119716091079117172192
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Rainier

In Rainier in September, humidity is 71%. With an average temperature of 16°C (62°F), this humidity feels like a warm, damp embrace, making it a bit uncomfortable for traveling unless you're accustomed to such conditions.

September Average Humidity in Rainier

This chart illustrates the average monthly humidity levels in Rainier, 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 Rainier 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 Rainier

In Rainier 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 Rainier.

Maximum UV Index Levels in Rainier for September

The chart shows the monthly maximum UV Index (UVI) for Rainier 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 Rainier typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec23569101087532
Data source: Rainier 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 Rainier Compares to Other Months

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

This table compares monthly weather conditions in Rainier, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather5°C (41°F)183 mm (7.2 inches)85%low
February Weather4°C (40°F)166 mm (6.5 inches)84%moderate
March Weather7°C (45°F)145 mm (5.7 inches)85%moderate
April Weather10°C (50°F)119 mm (4.7 inches)83%high
May Weather13°C (56°F)71 mm (2.8 inches)83%very high
June Weather16°C (61°F)59 mm (2.3 inches)83%very high
July Weather18°C (65°F)9 mm (0.4 inches)82%very high
August Weather19°C (66°F)9 mm (0.4 inches)74%very high
September Weather16°C (62°F)79 mm (3.1 inches)71%high
October Weather11°C (51°F)117 mm (4.6 inches)81%moderate
November Weather7°C (45°F)172 mm (6.8 inches)87%moderate
December Weather5°C (40°F)192 mm (7.6 inches)87%low

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