September Weather in Eureka, United States

Last updated: June 24, 2025

In September, the average temperature in Eureka, United States is a pleasant 18°C (65°F). However, temperatures can vary significantly, ranging from a chilly -4°C (25°F) to a scorching 36°C (97°F). Visitors can expect 12 mm (0.5 in) of precipitation over 2 days, with an average humidity level of 41%. Perfect for planning both outdoor adventures and cozy indoor activities!

September Temperature in Eureka

In September in Eureka, the average temperature is 18°C (65°F). Maximum temperatures can reach 36°C (97°F), while the minimum can drop as low as -4°C (25°F). Be prepared for a wide range of weather conditions 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 18°C (65°F), with highs reaching up to 36°C (97°F) and lows dropping to around -4°C (25°F).

Data source: Temperature data for Eureka generated using information from the Copernicus Climate Change Service.

September Precipitation in Eureka

In Eureka in September, the precipitation amount is 12 mm (0.5 in) over the course 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 12 mm (0.5 inches) of precipitation spread over approximately 2 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Eureka

In Eureka in September humidity is 41%. With an average temperature of 18°C (65°F), this humidity feels like a pleasant, crisp atmosphere, perfect for 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 41%, offering insight into how humid the weather typically is during this month.

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 reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. 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 10, which falls under the very high exposure category.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	-4°C (25°F)	29 mm (1.1 inches)	84%	moderate
February Weather	-3°C (27°F)	29 mm (1.1 inches)	87%	high
March Weather	1°C (35°F)	57 mm (2.3 inches)	80%	very high
April Weather	8°C (46°F)	39 mm (1.5 inches)	71%	very high
May Weather	12°C (55°F)	39 mm (1.5 inches)	55%	extreme
June Weather	20°C (68°F)	10 mm (0.4 inches)	51%	extreme
July Weather	25°C (77°F)	16 mm (0.6 inches)	41%	extreme
August Weather	24°C (75°F)	9 mm (0.3 inches)	32%	extreme
September Weather	18°C (65°F)	12 mm (0.5 inches)	41%	very high
October Weather	9°C (48°F)	22 mm (0.9 inches)	61%	high
November Weather	4°C (39°F)	22 mm (0.8 inches)	79%	moderate
December Weather	-3°C (26°F)	29 mm (1.1 inches)	83%	moderate