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September Weather in Eureka, United States

Last updated: June 24, 2025

In Eureka, United States, the average temperature in September hovers around 23°C (73°F). Expect a cool minimum of 5°C (41°F) and a warm maximum of 35°C (94°F) throughout the month. With 77 mm (3.0 in) of precipitation spread over 7 days, be prepared for some wet weather, and note that the average humidity stands at 67%.

September Temperature in Eureka

In September in Eureka, the average temperature is 23°C (73°F). Maximums can reach 35°C (94°F) and minimums can be as low as 5°C (41°F). Be sure to pack for both warm days and cooler evenings while traveling!

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 23°C (73°F), with highs reaching up to 35°C (94°F) and lows dropping to around 5°C (41°F).
JanFebMarAprMayJunJulAugSepOctNovDec343549556677807773584639
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 77 mm (3.0 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 77 mm (3.0 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec50408410020311493112771432831
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 67%. With an average temperature of 23°C (73°F), this humidity feels like a warm, enveloping blanket that makes the air feel thick and slightly sticky, which can be challenging for travelers who prefer cooler, drier conditions.

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 67%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec77%76%71%74%83%83%81%73%67%72%82%85%
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 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 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 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3679101111109753
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 Weather1°C (34°F)50 mm (2.0 inches)77%moderate
February Weather2°C (35°F)40 mm (1.6 inches)76%high
March Weather9°C (49°F)84 mm (3.3 inches)71%high
April Weather13°C (56°F)100 mm (3.9 inches)73%very high
May Weather19°C (66°F)203 mm (8.0 inches)83%very high
June Weather25°C (77°F)114 mm (4.5 inches)83%extreme
July Weather26°C (80°F)93 mm (3.7 inches)81%extreme
August Weather25°C (78°F)112 mm (4.4 inches)73%very high
September Weather23°C (73°F)77 mm (3.0 inches)67%very high
October Weather14°C (58°F)143 mm (5.6 inches)72%high
November Weather8°C (46°F)28 mm (1.1 inches)82%moderate
December Weather4°C (40°F)31 mm (1.2 inches)85%moderate

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