September weather forecastHerndon, IA
September
Weather in September
The first month of the autumn, September, is also a moderately hot month in Herndon, Iowa, with an average temperature fluctuating between 74.8°F (23.8°C) and 55.8°F (13.2°C).Temperature
As September takes hold, the average high-temperature is a still warm 74.8°F (23.8°C), nearly mirroring that of the previous month. During September, Herndon records an average temperature of 55.8°F (13.2°C) at night.Humidity
In September, the average relative humidity is 75%.Rainfall
In Herndon, in September, it is raining for 11.2 days, with typically 2.91" (74mm) of accumulated precipitation. Throughout the year, in Herndon, there are 125.7 rainfall days, and 26.5" (673mm) of precipitation is accumulated.Snowfall
June through September are months without snowfall.Daylight
In Herndon, the average length of the day in September is 12h and 28min.On the first day of September, sunrise is at 6:43 am and sunset at 7:50 pm. On the last day of the month, sunrise is at 7:14 am and sunset at 7:00 pm CDT.
Sunshine
In Herndon, the average sunshine in September is 9.3h.UV index
In September, the average daily maximum UV index is 4. A UV Index reading of 3 to 5 represents a medium health hazard from exposure to the Sun's UV radiation for average individuals.Note: In September, the maximum UV index of 4 translates into these guidelines:
Take heed. Individuals of lighter complexion can be burned in less than half an hour. The intensity of the Sun's UV radiation during midday suggests reducing time spent outdoors. Sunglasses that guard against UVA and UVB rays are pivotal in minimizing sun-induced ocular damage.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Herndon, IA
- Average high temperature in September: 74.8°F
The warmest month (with the highest average high temperature) is July (82°F).
The month with the lowest average high temperature is January (26.8°F).
- Average low temperature in September: 55.8°F
The month with the highest average low temperature is July (64.6°F).
The coldest month (with the lowest average low temperature) is January (13.5°F).
Average pressure in September
Herndon, IA
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).
Average wind speed in September
Herndon, IA
- Average wind speed in September: 8.3mph
The windiest month (with the highest average wind speed) is April (10.7mph).
The calmest months (with the lowest average wind speed) are July and August (7.1mph).
Average humidity in September
Herndon, IA
- Average humidity in September: 75%
The month with the highest relative humidity is January (84%).
The month with the lowest relative humidity is October (69%).
Average rainfall in September
Herndon, IA
- Average rainfall in September: 2.91"
The wettest month (with the highest rainfall) is May (4.06").
The driest month (with the least rainfall) is January (0.87").
Average rainfall days in September
Herndon, IA
- Average rainfall days in September: 11.2 days
The month with the highest number of rainy days is June (17.3 days).
The month with the least rainy days is February (3.4 days).
Average snowfall in September
Herndon, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (4.29").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Herndon, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (9.8 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Herndon, IA
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in September: 9h and 18min
The month with the most sunshine is July (Average sunshine: 10h and 12min).
The month with the least sunshine is January (Average sunshine: 4h and 12min).
Average sunshine days in September
Herndon, IA
- Average sunshine days in September: 17.2 days
The month with the most sunshine days is November (19.4 days).
The month with the least sunshine days is June (11.1 days).
Average UV index in September
Herndon, IA
- Average UV index in September: 4
The months with the highest UV index are June and July (UV index 6).
The months with the lowest UV index are January, February, October, November and December (UV index 2).
Average cloud cover in September
Herndon, IA
- Average cloud cover in September: 30
The month with the most cloud cover is January (Cloud cover 55).
The months with the least cloud cover are July and September (Cloud cover 30).
Average visibility in September
Herndon, IA
- Average visibility in September: 6mi
The months with the highest visibility are February, March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are January, July and August (5mi).
