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
September signifies a minor drop in average high-temperature, transitioning from a tropical 86.4°F (30.2°C) in August to a warm 80.8°F (27.1°C). Throughout September, the temperature falls to an average low of 61.5°F (16.4°C).Heat index
In September, the average heat index is calculated to be 84.2°F (29°C). One might feel worn out with persistent exposure and activity, resulting in heat cramps.In terms of the heat index, values are set with light wind and shade conditions in mind. Heat index values may rise by up to 15 Fahrenheit (8 Celsius) degrees when exposed to direct sunlight.
Note: The heat index, also known as 'real feel' or 'feels like', is an amalgamation of air temperature and humidity to express the equivalent perceived temperature. The impact of weather is individual, with diverse individuals experiencing it differently due to variations in body mass, height, and activity levels. It is noteworthy that being in direct sunlight can enhance the weather's impact, raising the heat index by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly meaningful for babies and toddlers. Young children typically face greater hazards than adults because they do not sweat as much. Their larger skin surface in comparison to their little bodies and the high heat production from their active nature compounds their vulnerability.
Humidity
In September, the average relative humidity in Herndon is 74%.Rainfall
September is the month with the least rainfall. Rain falls for 14.8 days and accumulates 2.17" (55mm) of precipitation.Snowfall
In Herndon, snow does not fall in May through September.Daylight
In September, the average length of the day is 12h and 24min.On the first day of September in Herndon, sunrise is at 6:21 am and sunset at 7:18 pm. On the last day of the month, sunrise is at 6:45 am and sunset at 6:34 pm CDT.
Sunshine
In Herndon, the average sunshine in September is 8.8h.UV index
In September, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a moderate health risk from exposure to the Sun's UV radiation for the average person.Note: In September, the maximum UV index of 5 translates into these guidelines:
Be vigilant - Preventing sunburn is recommended. Sun's radiation is most powerful around mid-day, so it's best to limit outdoor activities during this time. Limit sun-induced ocular harm with sunglasses that feature UVA and UVB filtration.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures in Herndon?
What is the average humidity in September in Herndon?
What is the driest month in Herndon?
How many days does it rain in September in Herndon?
When it does not snow in Herndon?
Does it snow in Herndon in September?
How many hours of daylight does Herndon have in September?
When are sunrise and sunset in September in Herndon?
How many hours of sunshine does Herndon have in September?
What is the UV index reading in September in Herndon?
Average temperature in September
Herndon, KY
- Average high temperature in September: 80.8°F
The warmest month (with the highest average high temperature) is July (87.4°F).
The month with the lowest average high temperature is January (42.6°F).
- Average low temperature in September: 61.5°F
The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (28.9°F).
Average pressure in September
Herndon, KY
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.17"Hg).
The month with the lowest atmospheric pressure is June (29.96"Hg).
Average wind speed in September
Herndon, KY
- Average wind speed in September: 5.8mph
The windiest months (with the highest average wind speed) are February and April (8.8mph).
The calmest month (with the lowest average wind speed) is July (5.2mph).
Average humidity in September
Herndon, KY
- Average humidity in September: 74%
The months with the highest relative humidity are March and May (79%).
The month with the lowest relative humidity is October (72%).
Average rainfall in September
Herndon, KY
- Average rainfall in September: 2.17"
The wettest month (with the highest rainfall) is February (4.06").
The driest month (with the least rainfall) is September (2.17").
Average rainfall days in September
Herndon, KY
- Average rainfall days in September: 14.8 days
The month with the highest number of rainy days is July (19.6 days).
The month with the least rainy days is November (10.8 days).
Average snowfall in September
Herndon, KY
- Average snowfall in September: 0"
The month with the highest snowfall is January (1.42").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Herndon, KY
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (4.9 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Herndon, KY
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 36min).
The month with the shortest days is December (Average daylight: 9h and 42min).
- Average sunshine in September: 8h and 5min
The month with the most sunshine is June (Average sunshine: 10h and 30min).
The month with the least sunshine is February (Average sunshine: 4h and 30min).
Average sunshine days in September
Herndon, KY
- Average sunshine days in September: 13.3 days
The months with the most sunshine days are October and November (17.8 days).
The month with the least sunshine days is July (8.6 days).
Average UV index in September
Herndon, KY
- Average UV index in September: 5
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February and December (UV index 2).
Average cloud cover in September
Herndon, KY
- Average cloud cover in September: 30
The month with the most cloud cover is February (Cloud cover 52).
The month with the least cloud cover is June (Cloud cover 29).
Average visibility in September
Herndon, KY
- 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).
Herndon, Kentucky, USA
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