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September Weather in Eureka, United States

Last updated: June 24, 2025

In September, the average temperature in Eureka, United States hovers around 11°C (53°F), showcasing a climate that can swing dramatically. Expect minimums as low as -4°C (25°F) and peak temperatures reaching 30°C (86°F). With an average humidity of 71% and 38 mm (1.5 in) of precipitation spread over 7 days, this month presents a dynamic weather experience that's both refreshing and occasionally challenging.

September Temperature in Eureka

In September in Eureka, the average temperature is 11°C (53°F), with maximums reaching up to 30°C (86°F) and minimums dropping as low as -4°C (25°F). Be prepared for a wide range of temperatures when traveling to Eureka during this time.

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

The chart illustrates September temperature patterns in Eureka, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Eureka, September typically has an average temperature of 11°C (53°F), with highs reaching up to 30°C (86°F) and lows dropping to around -4°C (25°F).
JanFebMarAprMayJunJulAugSepOctNovDec201629374856646353383023
Data source: Temperature data for Eureka 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 Eureka

In Eureka in September, the precipitation amount is 38 mm (1.5 in) over the course of 7 days.

September Precipitation Trends in Eureka

The chart displays monthly precipitation patterns in Eureka, 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 Eureka, September typically receives around 38 mm (1.5 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec517058666468243038706976
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Eureka

In Eureka in September humidity is 71%. With an average temperature of 11°C (53°F), this humidity feels like a damp chill that wraps around you, making outdoor activities less enjoyable and requiring extra layers to stay comfortable while exploring.

September Average Humidity in Eureka

This chart illustrates the average monthly humidity levels in Eureka, 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 Eureka is approximately 71%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec95%93%91%88%83%80%82%71%71%85%90%96%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Eureka

In Eureka 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 Eureka.

Maximum UV Index Levels in Eureka for September

The chart shows the monthly maximum UV Index (UVI) for Eureka 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 Eureka typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec235789997421
Data source: Eureka 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 Eureka Compares to Other Months

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

This table compares monthly weather conditions in Eureka, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-7°C (20°F)51 mm (2.0 inches)95%low
February Weather-9°C (16°F)70 mm (2.8 inches)93%moderate
March Weather-2°C (29°F)58 mm (2.3 inches)91%moderate
April Weather3°C (37°F)66 mm (2.6 inches)88%high
May Weather9°C (48°F)64 mm (2.5 inches)83%very high
June Weather13°C (56°F)68 mm (2.7 inches)80%very high
July Weather18°C (64°F)23 mm (0.9 inches)82%very high
August Weather17°C (63°F)29 mm (1.2 inches)71%very high
September Weather11°C (53°F)38 mm (1.5 inches)71%high
October Weather3°C (38°F)70 mm (2.7 inches)85%moderate
November Weather-1°C (31°F)69 mm (2.7 inches)90%low
December Weather-5°C (24°F)76 mm (3.0 inches)96%low

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