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 ushers in a minor alteration in Herndon's climate, with the average high-temperature moving from August's 80.2°F (26.8°C) to a still warm 73.8°F (23.2°C). September nights cool down to an average low-temperature of 53.6°F (12°C).Humidity
In September, the average relative humidity in Herndon is 79%.Rainfall
In September, in Herndon, the rain falls for 12.6 days. Throughout September, 2.13" (54mm) of precipitation is accumulated. Throughout the year, in Herndon, there are 165.3 rainfall days, and 30.55" (776mm) of precipitation is accumulated.Snowfall
In Herndon, snow does not fall in June through September.Daylight
In Herndon, the average length of the day in September is 12h and 27min.On the first day of the month, sunrise is at 6:35 am and sunset at 7:39 pm. On the last day of September, sunrise is at 7:03 am and sunset at 6:50 pm EDT.
Sunshine
The average sunshine in September in Herndon, Pennsylvania, is 8.8h.UV index
The average daily maximum UV index in September in Herndon is 4. A UV Index estimate of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV rays for average individuals.Note: In September, the maximum UV index of 4 suggests these recommendations:
Exercise prevention - Protecting skin and eyes from harm is required. Midday Sun has the strongest UV rays, making it crucial to limit exposure and find shade. Protect your eyes, ears, face, and neck from the Sun by wearing a wide-brimmed hat.
Frequently asked questions
What are September temperatures in Herndon?
What is the average humidity in September 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?
What is the average length of the day in September in Herndon?
When is the sunrise / sunset in September in Herndon?
How long on average sun shines in September in Herndon?
What is the UV index intensity in September in Herndon?
Average temperature in September
Herndon, PA
- Average high temperature in September: 73.8°F
The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (32.9°F).
- Average low temperature in September: 53.6°F
The month with the highest average low temperature is July (61.2°F).
The coldest month (with the lowest average low temperature) is January (20.1°F).
Average pressure in September
Herndon, PA
- Average pressure in September: 30.07"Hg
The month with the highest atmospheric pressure is November (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).
Average wind speed in September
Herndon, PA
- Average wind speed in September: 5.2mph
The windiest months (with the highest average wind speed) are March and April (7.8mph).
The calmest month (with the lowest average wind speed) is August (4.5mph).
Average humidity in September
Herndon, PA
- Average humidity in September: 79%
The month with the highest relative humidity is February (82%).
The month with the lowest relative humidity is April (76%).
Average rainfall in September
Herndon, PA
- Average rainfall in September: 2.13"
The wettest month (with the highest rainfall) is May (3.35").
The driest months (with the least rainfall) are February and November (2.09").
Average rainfall days in September
Herndon, PA
- Average rainfall days in September: 12.6 days
The month with the highest number of rainy days is May (18.4 days).
The month with the least rainy days is February (9 days).
Average snowfall in September
Herndon, PA
- Average snowfall in September: 0"
The month with the highest snowfall is February (5.67").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Herndon, PA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (11.3 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, PA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 8h and 5min
The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is February (Average sunshine: 4h and 12min).
Average sunshine days in September
Herndon, PA
- Average sunshine days in September: 15.4 days
The month with the most sunshine days is November (16.4 days).
The month with the least sunshine days is May (9.9 days).
Average UV index in September
Herndon, PA
- 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, March, November and December (UV index 2).
Average cloud cover in September
Herndon, PA
- Average cloud cover in September: 37
The month with the most cloud cover is February (Cloud cover 54).
The month with the least cloud cover is July (Cloud cover 32).
Average visibility in September
Herndon, PA
- Average visibility in September: 5mi
The months with the highest visibility are March, April, June, July and November (6mi).
The months with the lowest visibility are January, February, May, August, September, October and December (5mi).
Herndon, Pennsylvania, USA
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