September Weather in Umatilla, United States

Last updated: June 24, 2025

In September, the average temperature in Umatilla, United States hovers around 27°C (81°F), creating a warm atmosphere for visitors. Expect a minimum of 18°C (65°F) and a maximum of 36°C (97°F), which offers a wide range of pleasant experiences. However, be prepared for some rainfall, as 153 mm (6.0 in) of precipitation is expected over 18 days, contributing to an average humidity of 83%.

September Temperature in Umatilla

In September in Umatilla, the average temperature is 27°C (81°F). The maximum can reach 36°C (97°F), while the minimum can dip to 18°C (65°F). This makes it an ideal time for travelers seeking warm and pleasant weather.

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

The chart illustrates September temperature patterns in Umatilla, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Umatilla, September typically has an average temperature of 27°C (81°F), with highs reaching up to 36°C (97°F) and lows dropping to around 18°C (65°F).

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

September Precipitation in Umatilla

In Umatilla in September, the total precipitation amount reaches 153 mm (6.0 in) over the course of 18 days.

September Precipitation Trends in Umatilla

The chart displays monthly precipitation patterns in Umatilla, 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 Umatilla, September typically receives around 153 mm (6.0 inches) of precipitation spread over approximately 18 days.

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

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Millimeters (mm) Inches (in)

September Humidity in Umatilla

In Umatilla in September humidity is 83%. With an average temperature of 27°C (81°F), this humidity feels like a warm blanket enveloping you, making sightseeing and outdoor activities feel more exhausting and requiring frequent breaks to relax in the shade or cool off.

September Average Humidity in Umatilla

This chart illustrates the average monthly humidity levels in Umatilla, 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 Umatilla is approximately 83%, 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 Umatilla

In Umatilla in September, the maximum UV index reaches 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, you can check the Hourly UV Index in Umatilla.

Maximum UV Index Levels in Umatilla for September

The chart shows the monthly maximum UV Index (UVI) for Umatilla 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 Umatilla typically reaches 11, which falls under the extreme exposure category.

Data source: Umatilla 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 Umatilla Compares to Other Months

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

This table compares monthly weather conditions in Umatilla, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	15°C (59°F)	47 mm (1.9 inches)	83%	moderate
February Weather	18°C (65°F)	57 mm (2.2 inches)	80%	very high
March Weather	19°C (67°F)	25 mm (1.0 inches)	75%	very high
April Weather	22°C (72°F)	80 mm (3.2 inches)	70%	extreme
May Weather	25°C (77°F)	97 mm (3.8 inches)	68%	extreme
June Weather	27°C (81°F)	190 mm (7.5 inches)	75%	extreme
July Weather	27°C (82°F)	221 mm (8.7 inches)	79%	extreme
August Weather	28°C (82°F)	203 mm (8.0 inches)	81%	extreme
September Weather	27°C (81°F)	153 mm (6.0 inches)	83%	extreme
October Weather	25°C (77°F)	80 mm (3.1 inches)	81%	very high
November Weather	19°C (67°F)	58 mm (2.3 inches)	82%	high
December Weather	17°C (62°F)	71 mm (2.8 inches)	84%	moderate