September Weather in Knoxville, United States

Last updated: June 24, 2025

In September, the average temperature in Knoxville, United States hovers around 20°C (69°F). Expect a minimum of 5°C (42°F) and a potential maximum of 34°C (94°F). During this month, precipitation averages 99 mm (3.9 in) across 8 days, while the air carries a humidity level of approximately 78%.

September Temperature in Knoxville

In September in Knoxville, the average temperature is 20°C (69°F). Maximum temperatures can reach 34°C (94°F), while minimums can drop to as low as 5°C (42°F). Be sure to pack for a range of weather conditions, from warm days to cooler evenings, as you explore Knoxville.

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

The chart illustrates September temperature patterns in Knoxville, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Knoxville, September typically has an average temperature of 20°C (69°F), with highs reaching up to 34°C (94°F) and lows dropping to around 5°C (42°F).

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

September Precipitation in Knoxville

In Knoxville in September, the precipitation amount is 99 mm (3.9 in) spread over 8 days.

September Precipitation Trends in Knoxville

The chart displays monthly precipitation patterns in Knoxville, 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 Knoxville, September typically receives around 99 mm (3.9 inches) of precipitation spread over approximately 8 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 Knoxville

In Knoxville in September, humidity is 78%. With an average temperature of 20°C (69°F), this humidity feels like a warm, enveloping blanket, making travel somewhat uncomfortable as sweat clings to your skin and the air feels thick and heavy, urging you to seek out shaded areas and refreshing drinks.

September Average Humidity in Knoxville

This chart illustrates the average monthly humidity levels in Knoxville, 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 Knoxville is approximately 78%, 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 Knoxville

In Knoxville 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 Knoxville.

Maximum UV Index Levels in Knoxville for September

The chart shows the monthly maximum UV Index (UVI) for Knoxville 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 Knoxville typically reaches 8, which falls under the very high exposure category.

Data source: Knoxville 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 Knoxville Compares to Other Months

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

This table compares monthly weather conditions in Knoxville, 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 (26°F)	57 mm (2.2 inches)	81%	moderate
February Weather	-2°C (28°F)	65 mm (2.6 inches)	81%	moderate
March Weather	5°C (41°F)	105 mm (4.1 inches)	81%	high
April Weather	10°C (50°F)	111 mm (4.4 inches)	82%	very high
May Weather	17°C (63°F)	160 mm (6.3 inches)	78%	very high
June Weather	23°C (74°F)	152 mm (6.0 inches)	81%	extreme
July Weather	25°C (77°F)	108 mm (4.2 inches)	79%	very high
August Weather	23°C (74°F)	67 mm (2.6 inches)	77%	very high
September Weather	20°C (69°F)	99 mm (3.9 inches)	78%	very high
October Weather	13°C (55°F)	126 mm (5.0 inches)	78%	high
November Weather	4°C (40°F)	52 mm (2.1 inches)	87%	moderate
December Weather	1°C (33°F)	50 mm (2.0 inches)	84%	low