Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
With September's onset, the weather reveals a slight temperature decrease, transitioning from 81.5°F (27.5°C) in August to a still warm 75.7°F (24.3°C). In Knoxville, the September nights cool down to an average low of 56.1°F (13.4°C).Humidity
In September, the average relative humidity is 77%.Rainfall
In Knoxville, Iowa, during September, the rain falls for 9.8 days and regularly aggregates up to 1.5" (38mm) of precipitation. In Knoxville, Iowa, during the entire year, the rain falls for 115.3 days and collects up to 13.31" (338mm) of precipitation.Snowfall
In Knoxville, snow does not fall in June through September.Daylight
The average length of the day in September is 12h and 28min.On the first day of the month, sunrise is at 6:39 am and sunset at 7:44 pm. On the last day of September, sunrise is at 7:08 am and sunset at 6:55 pm CDT.
Sunshine
In Knoxville, the average sunshine in September is 9.4h.UV index
The average daily maximum UV index in September in Knoxville is 4. A UV Index value of 3 to 5 symbolizes a medium vulnerability from unprotected exposure to Sun's UV rays for average individuals.Note: The maximum daily UV index of 4 during September translates into the following directions:
Be vigilant - Preventing sunburn is recommended. The midday Sun can be dangerous due to its intense radiation; always find shade and reduce exposure. Protect your eyes, ears, face, and neck from the Sun by wearing a wide-brimmed hat.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in Knoxville in September?
What is the average humidity in September in Knoxville?
How many days does it rain in September in Knoxville?
When it does not snow in Knoxville?
Does it snow in Knoxville in September?
How many hours of daylight does Knoxville have in September?
What time are sunrise and sunset in September in Knoxville?
How many hours of sunshine does Knoxville have in September?
What is the UV index intensity in September in Knoxville?
Average temperature in September
Knoxville, IA
- Average high temperature in September: 75.7°F
The warmest month (with the highest average high temperature) is July (82.8°F).
The month with the lowest average high temperature is January (28.6°F).
- Average low temperature in September: 56.1°F
The month with the highest average low temperature is July (65.5°F).
The coldest month (with the lowest average low temperature) is January (15.1°F).
Average pressure in September
Knoxville, IA
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
Knoxville, IA
- Average wind speed in September: 8mph
The windiest month (with the highest average wind speed) is January (10.5mph).
The calmest month (with the lowest average wind speed) is August (6.8mph).
Average humidity in September
Knoxville, IA
- Average humidity in September: 77%
The month with the highest relative humidity is January (83%).
The month with the lowest relative humidity is October (71%).
Average rainfall in September
Knoxville, IA
- Average rainfall in September: 1.5"
The wettest month (with the highest rainfall) is May (2.24").
The driest months (with the least rainfall) are February and December (0.47").
Average rainfall days in September
Knoxville, IA
- Average rainfall days in September: 9.8 days
The month with the highest number of rainy days is May (15.3 days).
The month with the least rainy days is February (3.9 days).
Average snowfall in September
Knoxville, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (2.24").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Knoxville, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (8.7 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Knoxville, IA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 9h and 2min
The month with the most sunshine is July (Average sunshine: 10h and 30min).
The month with the least sunshine is January (Average sunshine: 4h and 18min).
Average sunshine days in September
Knoxville, IA
- Average sunshine days in September: 18.4 days
The months with the most sunshine days are November and December (20.5 days).
The month with the least sunshine days is June (11.6 days).
Average UV index in September
Knoxville, IA
- Average UV index in September: 4
The months with the highest UV index are June, July and August (UV index 6).
The month with the lowest UV index is January (UV index 1).
Average cloud cover in September
Knoxville, IA
- Average cloud cover in September: 29
The month with the most cloud cover is January (Cloud cover 53).
The months with the least cloud cover are July, August and September (Cloud cover 29).
Average visibility in September
Knoxville, IA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Knoxville, Iowa, USA
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