September Weather in Knoxville, United States

Last updated: June 24, 2025

In Knoxville, United States, the average temperature in September hovers around 25°C (78°F). However, be prepared for a range, with minimums plummeting to 12°C (54°F) and maximums soaring to 37°C (98°F). During this month, you'll encounter about 96 mm (3.8 in) of precipitation spread over 8 days, along with a notably high average humidity of 82%.

September Temperature in Knoxville

In September in Knoxville, the average temperature is 25°C (78°F). Maximums can reach 37°C (98°F) and minimums can be as low as 12°C (54°F). This range makes it a perfect time to explore and enjoy outdoor activities in 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 25°C (78°F), with highs reaching up to 37°C (98°F) and lows dropping to around 12°C (54°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 96 mm (3.8 in) over the course of 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 96 mm (3.8 inches) of precipitation spread over approximately 8 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 Knoxville

In Knoxville in September, humidity is 82%. With an average temperature of 25°C (78°F), this humidity feels like a warm, heavy blanket wrapping around you, making outdoor activities a bit more challenging and encouraging you to seek shade or a cool spot during your travels.

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 82%, 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 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 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 10, 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	9°C (49°F)	110 mm (4.3 inches)	86%	moderate
February Weather	13°C (55°F)	119 mm (4.7 inches)	84%	high
March Weather	15°C (59°F)	80 mm (3.2 inches)	83%	very high
April Weather	18°C (65°F)	95 mm (3.8 inches)	81%	very high
May Weather	23°C (74°F)	83 mm (3.3 inches)	81%	extreme
June Weather	26°C (79°F)	113 mm (4.4 inches)	81%	extreme
July Weather	27°C (82°F)	95 mm (3.7 inches)	83%	extreme
August Weather	27°C (81°F)	118 mm (4.6 inches)	81%	extreme
September Weather	25°C (78°F)	96 mm (3.8 inches)	82%	very high
October Weather	21°C (69°F)	100 mm (3.9 inches)	78%	very high
November Weather	13°C (56°F)	76 mm (3.0 inches)	86%	high
December Weather	11°C (51°F)	121 mm (4.7 inches)	89%	moderate