September Weather in Umatilla, United States

Last updated: June 24, 2025

In Umatilla, United States, the average temperature in September hovers around 20°C (69°F), making it a pleasant time to visit. However, don't be surprised by the temperature range — it can dip as low as 5°C (42°F) or soar up to 39°C (102°F). Expect some light rain, with precipitation totaling 9 mm (0.4 in) over 2 days. Overall, the average humidity stands at a comfortable 58%, ensuring a refreshing atmosphere for your adventures!

September Temperature in Umatilla

In September in Umatilla, the average temperature is 20°C (69°F). Maximum can reach 39°C (102°F) and minimum can be as low as 5°C (42°F). Travelers should be prepared for a wide range of temperatures and pack accordingly.

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 20°C (69°F), with highs reaching up to 39°C (102°F) and lows dropping to around 5°C (42°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 precipitation amount is 9 mm (0.4 in) over the course of 2 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 9 mm (0.4 inches) of precipitation spread over approximately 2 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 58%. With an average temperature of 20°C (69°F), this humidity feels like a refreshing balmy embrace, making it quite pleasant for traveling as long as you stay hydrated and take occasional breaks in the shade.

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 58%, 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 is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, 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 7, which falls under the high 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	2°C (36°F)	35 mm (1.4 inches)	86%	low
February Weather	3°C (37°F)	46 mm (1.8 inches)	86%	moderate
March Weather	8°C (46°F)	30 mm (1.2 inches)	85%	moderate
April Weather	13°C (55°F)	24 mm (0.9 inches)	83%	high
May Weather	18°C (65°F)	15 mm (0.6 inches)	77%	very high
June Weather	23°C (73°F)	8 mm (0.3 inches)	81%	very high
July Weather	27°C (81°F)	0 mm (0.0 inches)	76%	very high
August Weather	26°C (79°F)	4 mm (0.1 inches)	60%	very high
September Weather	20°C (69°F)	9 mm (0.4 inches)	58%	high
October Weather	12°C (54°F)	26 mm (1.0 inches)	75%	moderate
November Weather	6°C (43°F)	34 mm (1.3 inches)	85%	moderate
December Weather	2°C (37°F)	33 mm (1.3 inches)	87%	low