September Weather in Eureka, United States

Last updated: June 24, 2025

The average temperature in Eureka, United States during September is a mild 16°C (62°F). However, be prepared for temperature fluctuations, as it can drop to a chilly 1°C (34°F) or rise to a warm 34°C (94°F). Expect precipitation measuring 69 mm (2.7 in) over about 7 days, alongside an average humidity level of 77%. Stay comfortable and prepared for whatever the weather brings!

September Temperature in Eureka

In September in Eureka, the average temperature is 16°C (62°F). The maximum can reach up to 34°C (94°F), while the minimum can drop as low as 1°C (34°F). Be prepared for a range of weather conditions if you plan to travel 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 16°C (62°F), with highs reaching up to 34°C (94°F) and lows dropping to around 1°C (34°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 69 mm (2.7 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 69 mm (2.7 inches) of precipitation spread over approximately 7 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 77%. With an average temperature of 16°C (62°F), this humidity feels like a warm, enveloping blanket that can make outdoor activities feel heavy and draining, so travelers may want to plan for breaks in shaded areas and stay hydrated.

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 77%, 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 is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to 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 8, 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	-10°C (15°F)	14 mm (0.6 inches)	81%	low
February Weather	-11°C (13°F)	17 mm (0.7 inches)	85%	moderate
March Weather	-1°C (30°F)	29 mm (1.1 inches)	76%	moderate
April Weather	4°C (40°F)	43 mm (1.7 inches)	79%	high
May Weather	13°C (56°F)	57 mm (2.2 inches)	76%	very high
June Weather	21°C (70°F)	59 mm (2.3 inches)	81%	very high
July Weather	23°C (74°F)	63 mm (2.5 inches)	82%	very high
August Weather	21°C (70°F)	102 mm (4.0 inches)	82%	very high
September Weather	16°C (62°F)	69 mm (2.7 inches)	77%	very high
October Weather	7°C (44°F)	63 mm (2.5 inches)	76%	moderate
November Weather	0°C (32°F)	14 mm (0.5 inches)	84%	moderate
December Weather	-6°C (22°F)	27 mm (1.1 inches)	81%	low