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September Weather in Stillwater, United States

Last updated: June 24, 2025

In September, the average temperature in Stillwater, United States is a pleasant 24°C (76°F). However, be prepared for a temperature range that can dip as low as 7°C (45°F) and soar up to 38°C (100°F). Expect about 81 mm (3.2 in) of precipitation spread over 7 days, with an average humidity of 64%.

September Temperature in Stillwater

In September in Stillwater, the average temperature is 24°C (76°F). Maximum temperatures can reach 38°C (100°F), while minimums can drop as low as 7°C (45°F). This diverse temperature range makes Stillwater an ideal destination for travelers seeking both warm days and cooler evenings.

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

The chart illustrates September temperature patterns in Stillwater, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Stillwater, September typically has an average temperature of 24°C (76°F), with highs reaching up to 38°C (100°F) and lows dropping to around 7°C (45°F).
JanFebMarAprMayJunJulAugSepOctNovDec394053596979828176625043
Data source: Temperature data for Stillwater 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 Stillwater

In Stillwater in September, the precipitation amount is 81 mm (3.2 in) over a period of 7 days.

September Precipitation Trends in Stillwater

The chart displays monthly precipitation patterns in Stillwater, 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 Stillwater, September typically receives around 81 mm (3.2 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec5745861231431119091811083635
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Stillwater

In Stillwater in September, humidity is 64%. With an average temperature of 24°C (76°F), this humidity feels like a warm, sticky embrace, making travel slightly uncomfortable but still enjoyable, as you may find yourself yearning for a refreshing breeze or a quick dip in the water.

September Average Humidity in Stillwater

This chart illustrates the average monthly humidity levels in Stillwater, 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 Stillwater is approximately 64%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec79%78%75%75%83%82%78%68%64%71%82%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Stillwater

In Stillwater in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Stillwater.

Maximum UV Index Levels in Stillwater for September

The chart shows the monthly maximum UV Index (UVI) for Stillwater 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 Stillwater typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec46710101111109753
Data source: Stillwater 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 Stillwater Compares to Other Months

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

This table compares monthly weather conditions in Stillwater, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather4°C (39°F)57 mm (2.3 inches)79%moderate
February Weather5°C (41°F)45 mm (1.8 inches)78%high
March Weather12°C (53°F)86 mm (3.4 inches)75%high
April Weather15°C (59°F)123 mm (4.8 inches)75%very high
May Weather21°C (70°F)143 mm (5.6 inches)83%very high
June Weather26°C (79°F)110 mm (4.3 inches)81%extreme
July Weather28°C (83°F)90 mm (3.6 inches)78%extreme
August Weather27°C (81°F)91 mm (3.6 inches)68%very high
September Weather24°C (76°F)81 mm (3.2 inches)64%very high
October Weather16°C (62°F)108 mm (4.3 inches)71%high
November Weather10°C (50°F)36 mm (1.4 inches)82%moderate
December Weather6°C (44°F)35 mm (1.4 inches)87%moderate

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