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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 21°C (69°F), making it a comfortable time of year. However, be prepared for temperature fluctuations, as it can dip to a chilly -1°C (31°F) or soar up to a sweltering 37°C (99°F). During this month, expect about 21 mm (0.8 in) of precipitation spread over 2 days, contributing to an average humidity of 47%.

September Temperature in Eureka

In September in Eureka, the average temperature is 21°C (69°F), with maximums reaching up to 37°C (99°F) and minimums dipping as low as -1°C (31°F). Travelers should be prepared for a wide range of temperatures during this time, ensuring they pack accordingly for both warm days and cooler nights.

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 21°C (69°F), with highs reaching up to 37°C (99°F) and lows dropping to around -1°C (31°F).
JanFebMarAprMayJunJulAugSepOctNovDec253039496074827969514127
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 21 mm (0.8 in) over a period of 2 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 21 mm (0.8 inches) of precipitation spread over approximately 2 days.
JanFebMarAprMayJunJulAugSepOctNovDec45486047421092021352742
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 47%. With an average temperature of 21°C (69°F), this humidity feels like a comfortable and refreshing environment for traveling, making it ideal for exploring the sights without feeling too hot or sticky.

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 47%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec88%88%77%70%54%45%37%34%47%67%82%87%
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.
JanFebMarAprMayJunJulAugSepOctNovDec46710111212119753
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-4°C (25°F)44 mm (1.8 inches)87%moderate
February Weather-1°C (30°F)48 mm (1.9 inches)88%high
March Weather4°C (39°F)60 mm (2.4 inches)77%high
April Weather10°C (50°F)47 mm (1.8 inches)69%very high
May Weather15°C (60°F)42 mm (1.6 inches)54%extreme
June Weather23°C (74°F)10 mm (0.4 inches)45%extreme
July Weather28°C (82°F)9 mm (0.3 inches)37%extreme
August Weather26°C (79°F)20 mm (0.8 inches)34%extreme
September Weather21°C (69°F)21 mm (0.8 inches)47%very high
October Weather10°C (51°F)35 mm (1.4 inches)67%high
November Weather5°C (41°F)27 mm (1.1 inches)82%moderate
December Weather-3°C (28°F)42 mm (1.6 inches)87%moderate

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