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September Weather in Knoxville, United States

Last updated: June 24, 2025

In September, the average temperature in Knoxville, United States is a mild 23°C (74°F). This period can bring a range of temperatures, with lows of 9°C (48°F) and highs soaring up to 36°C (97°F). Expect a precipitation total of 91 mm (3.6 in) over approximately 9 days, and don't forget that the average humidity is around 76%, providing a notable atmosphere throughout the month.

September Temperature in Knoxville

In September in Knoxville, the average temperature is 23°C (74°F). Maximums can reach 36°C (97°F) while minimums can drop to as low as 9°C (48°F). This varied climate makes Knoxville an ideal destination for travelers seeking both warmth and cooler moments throughout the day.

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 23°C (74°F), with highs reaching up to 36°C (97°F) and lows dropping to around 9°C (48°F).
JanFebMarAprMayJunJulAugSepOctNovDec414652596975797773634945
Data source: Temperature data for Knoxville generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Knoxville

In Knoxville in September, the precipitation amount is 91 mm (3.6 in) spread over 9 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 91 mm (3.6 inches) of precipitation spread over approximately 9 days.
JanFebMarAprMayJunJulAugSepOctNovDec981721551321061121201269111679132
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Knoxville

In Knoxville in September humidity is 76%. With an average temperature of 23°C (74°F), this humidity feels like a warm, thick blanket wrapping around you, making outdoor exploration feel a bit sluggish and requiring frequent breaks for hydration and respite from the heat.

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 76%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%86%86%82%85%85%83%76%76%80%88%88%
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 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For 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 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec36810111111109753
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.
 TemperaturePrecipitationHumidityUV
January Weather5°C (41°F)98 mm (3.9 inches)86%moderate
February Weather8°C (46°F)172 mm (6.8 inches)86%high
March Weather11°C (52°F)155 mm (6.1 inches)86%very high
April Weather15°C (59°F)132 mm (5.2 inches)82%very high
May Weather21°C (69°F)106 mm (4.2 inches)85%extreme
June Weather24°C (75°F)112 mm (4.4 inches)85%extreme
July Weather26°C (79°F)120 mm (4.7 inches)83%extreme
August Weather25°C (78°F)126 mm (5.0 inches)76%very high
September Weather23°C (74°F)91 mm (3.6 inches)76%very high
October Weather17°C (63°F)116 mm (4.6 inches)80%high
November Weather9°C (49°F)79 mm (3.1 inches)88%moderate
December Weather7°C (45°F)132 mm (5.2 inches)88%moderate

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