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September Weather in Riley, United States

Last updated: June 24, 2025

In Riley, United States, the average temperature in September hovers around 23°C (73°F). During this time, you can expect a minimum of 6°C (42°F) and a maximum of 37°C (99°F). With an average precipitation of 64 mm (2.5 in) spread over 8 days, the average humidity sits at a comfortable 71%. Prepare for a month that balances warmth and refreshing rain!

September Temperature in Riley

In September in Riley, the average temperature is 23°C (73°F), with maximums reaching up to 37°C (99°F) and minimums dropping as low as 6°C (42°F). This variability makes it essential to pack layers for your travels, ensuring you're prepared for both warm days and cooler nights.

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

The chart illustrates September temperature patterns in Riley, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Riley, September typically has an average temperature of 23°C (73°F), with highs reaching up to 37°C (99°F) and lows dropping to around 6°C (42°F).
JanFebMarAprMayJunJulAugSepOctNovDec313246546678817773574437
Data source: Temperature data for Riley 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 Riley

In Riley in September, the precipitation amount is 64 mm (2.5 in) over the course of 8 days.

September Precipitation Trends in Riley

The chart displays monthly precipitation patterns in Riley, 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 Riley, September typically receives around 64 mm (2.5 inches) of precipitation spread over approximately 8 days.
JanFebMarAprMayJunJulAugSepOctNovDec30288467185798011964983327
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Riley

In Riley in September humidity is 71%. With an average temperature of 23°C (73°F), this humidity feels like a warm, sticky embrace, making outdoor exploration slightly uncomfortable but still manageable if you stay hydrated and plan for breaks in shaded areas.

September Average Humidity in Riley

This chart illustrates the average monthly humidity levels in Riley, 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 Riley is approximately 71%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec76%78%70%73%82%82%81%78%71%71%81%84%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Riley

In Riley 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 Riley.

Maximum UV Index Levels in Riley for September

The chart shows the monthly maximum UV Index (UVI) for Riley 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 Riley typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3569101111109643
Data source: Riley 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 Riley Compares to Other Months

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

This table compares monthly weather conditions in Riley, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (31°F)30 mm (1.2 inches)76%moderate
February Weather0°C (32°F)28 mm (1.1 inches)77%moderate
March Weather8°C (46°F)84 mm (3.3 inches)70%high
April Weather12°C (55°F)67 mm (2.6 inches)73%very high
May Weather19°C (66°F)185 mm (7.3 inches)82%very high
June Weather26°C (79°F)79 mm (3.1 inches)82%extreme
July Weather27°C (81°F)80 mm (3.1 inches)81%extreme
August Weather25°C (78°F)119 mm (4.7 inches)78%very high
September Weather23°C (73°F)64 mm (2.5 inches)71%very high
October Weather14°C (57°F)98 mm (3.9 inches)71%high
November Weather7°C (44°F)33 mm (1.3 inches)81%moderate
December Weather3°C (37°F)27 mm (1.0 inches)84%moderate

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