September weather forecast
Herndon, VA

Weather in September

The first month of the autumn, September, is still a warm month in Herndon, Virginia, with an average temperature ranging between min 59.7°F (15.4°C) and max 78.3°F (25.7°C).

Temperature

In Herndon, the average high-temperature in September slightly decreases from 85.6°F (29.8°C) in August to a still moderately hot 78.3°F (25.7°C). In September, in Herndon, the average low-temperature is 59.7°F (15.4°C).

Humidity

In Herndon, the average relative humidity in September is 75%.

Rainfall

September is the month with the least rainfall. Rain falls for 12.6 days and accumulates 1.93" (49mm) of precipitation.

Snowfall

In Herndon, snow does not fall in May through October.

Daylight

In September, the average length of the day is 12h and 26min.
On the first day of the month, sunrise is at 6:38 am and sunset at 7:40 pm. On the last day of September, sunrise is at 7:04 am and sunset at 6:54 pm EDT.

Sunshine

In September, the average sunshine in Herndon is 8.7h.

UV index

The average daily maximum UV index in September is 5. A UV Index of 3 to 5 symbolizes a medium health hazard from unprotected exposure to Sun's UV rays for the average person.
Note: The average daily UV index of 5 in September transform into the following instructions:
Take precautions - Protection against skin and eye damage is obliged. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
[Resources]

FAQ

What is the temperature in September in Herndon?

The average high-temperature, in September, in Herndon, Virginia, is 78.3°F (25.7°C), while the average low-temperature is 59.7°F (15.4°C). in August, the average heat index (a.k.a. 'feels like', 'apparent temperature'), which combines relative humidity and air temperature, is calculated to be 95°F (35°C).

What is the average humidity in September in Herndon?

The average relative humidity in September is 75%.

What is the driest month in Herndon?

The month with the least rainfall in Herndon, Virginia, is September, when the rain falls for 12.6 days and typically collects 1.93" (49mm) of precipitation.

How many days does it rain in September in Herndon?

In Herndon, during September, the rain falls for 12.6 days and regularly aggregates up to 1.93" (49mm) of precipitation.

When it does not snow in Herndon?

May through October are months without snowfall in Herndon.

How many hours of daylight does Herndon have in September?

In September, the average day length in Herndon is 12h and 26min.

When are sunrise and sunset in September in Herndon?

On the first day of September in Herndon, Virginia, sunrise is at 6:38 am and sunset at 7:40 pm. On the last day of the month, sunrise is at 7:04 am and sunset at 6:54 pm EDT.

How many hours of sunshine does Herndon have in September?

In September, the average sunshine duration is 8.7h.

What is the UV index intensity in September in Herndon?

In Herndon, the average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a moderate health threat from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Herndon, VA

Average temperature in September - Herndon, VA
  • Average high temperature in September: 78.3°F

The warmest month (with the highest average high temperature) is July (87.8°F).
The month with the lowest average high temperature is January (39.7°F).

  • Average low temperature in September: 59.7°F

The month with the highest average low temperature is July (67.3°F).
The coldest month (with the lowest average low temperature) is January (25.9°F).

[Resources]

Average pressure in September
Herndon, VA

Average pressure in September - Herndon, VA
  • Average pressure in September: 30.05"Hg

The month with the highest atmospheric pressure is November (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.95"Hg).

[Resources]

Average wind speed in September
Herndon, VA

Average wind speed in September - Herndon, VA
  • Average wind speed in September: 5.3mph

The windiest month (with the highest average wind speed) is March (7.5mph).
The calmest month (with the lowest average wind speed) is August (4.7mph).

[Resources]

Average humidity in September
Herndon, VA

Average humidity in September - Herndon, VA
  • Average humidity in September: 75%

The month with the highest relative humidity is December (78%).
The month with the lowest relative humidity is July (70%).

[Resources]

Average rainfall in September
Herndon, VA

Average rainfall in September - Herndon, VA
  • Average rainfall in September: 1.93"

The wettest month (with the highest rainfall) is August (3.78").
The driest month (with the least rainfall) is September (1.93").

[Resources]

Average rainfall days in September
Herndon, VA

Average rainfall days in September - Herndon, VA
  • Average rainfall days in September: 12.6 days

The month with the highest number of rainy days is May (17.5 days).
The month with the least rainy days is January (9.3 days).

[Resources]

Average snowfall in September
Herndon, VA

Average snowfall in September - Herndon, VA
  • Average snowfall in September: 0"

The month with the highest snowfall is January (3.54").
The months with the least snowfall are May, June, July, August, September and October (0").

[Resources]

Average snowfall days in September
Herndon, VA

Average snowfall days in September - Herndon, VA
  • Average snowfall days in September: 0 days

The months with the highest number of snowfall days are January and February (5.1 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

[Resources]

Average daylight in September /
Average sunshine in September
Herndon, VA

Average daylight in September / Average sunshine in September - Herndon, VA
  • Average daylight in September: 12h and 26min

The month with the longest days is June (Average daylight: 14h and 52min).
The month with the shortest days is December (Average daylight: 9h and 29min).

  • Average sunshine in September: 8h and 42min

The month with the most sunshine is July (Average sunshine: 10h and 42min).
The months with the least sunshine are January, February and December (Average sunshine: 5h and 0min).

[Resources]

Average sunshine days in September
Herndon, VA

Average sunshine days in September - Herndon, VA
  • Average sunshine days in September: 15.9 days

The month with the most sunshine days is November (19.5 days).
The month with the least sunshine days is July (11.8 days).

[Resources]

Average UV index in September
Herndon, VA

Average UV index in September - Herndon, VA
  • 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, November and December (UV index 2).

[Resources]

Average cloud cover in September
Herndon, VA

Average cloud cover in September - Herndon, VA
  • Average cloud cover in September: 38

The month with the most cloud cover is March (Cloud cover 48).
The month with the least cloud cover is July (Cloud cover 31).

[Resources]

Average visibility in September
Herndon, VA

Average visibility in September - Herndon, VA
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is May (5mi).

[Resources]

Weather forecast for your location

1. Click Locate me button
2. Allow the app to use your location
* you will be automatically redirected to the weather forecast for your location