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
The start of September involves a subtle temperature drop, shifting from a hot 88.3°F (31.3°C) in August to a warm 81.3°F (27.4°C). Throughout the month of September, the nighttime temperature dips to an average of 62.6°F (17°C).Heat index
In September, the heat index is computed to be a hot 86°F (30°C). Enduring exposure and ongoing activity could cause a sense of fatigue and subsequent heat cramps.Metrics for the heat index primarily focus on shaded spots and light wind conditions. Direct sunlight has the potential to heighten heat index values by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'apparent temperature', represents the fusion of temperature and moisture in the air to suggest how warm it feels. This effect is personal, influenced by the individual's physical activity and heat sensitivity, shaped by factors including wind, attire, and metabolic variations. When in direct sunlight, one should be cautious as it can raise the heat index by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly meaningful for babies and toddlers. Children often do not understand the need to rest and hydrate. Thirst is a late manifestation of dehydration - therefore, it is essential to stay hydrated, particularly during prolonged physical activities.
Humidity
In September, the average relative humidity in Roslyn Hills is 73%.Rainfall
September is the month with the least rainfall. Rain falls for 12.5 days and accumulates 1.65" (42mm) of precipitation.Snowfall
In Roslyn Hills, snow does not fall in May through October.Daylight
The average length of the day in September is 12h and 25min.On the first day of September, sunrise is at 6:41 am and sunset at 7:38 pm. On the last day of the month, sunrise is at 7:05 am and sunset at 6:54 pm EDT.
Sunshine
The average sunshine in September is 8.7h.UV index
In Roslyn Hills, the average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a moderate health risk from exposure to the Sun's UV radiation for average individuals.Note: In September, the maximum UV index of 5 translates into these guidelines:
Undertake precautions - Guarding against sun damage is counselled. The solar radiation around mid-day is intense; avoid the Sun and stay safe. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the average September temperature?
What is the average humidity in September?
What is the driest month?
How many days does it rain in September?
When it does not snow?
How many hours of daylight does Roslyn Hills have in September?
When is the sunrise / sunset in September?
How many hours of sunshine does Roslyn Hills have in September?
What is the UV index intensity in September in Roslyn Hills?
Average temperature in September
Roslyn Hills, VA
- Average high temperature in September: 81.3°F
The warmest month (with the highest average high temperature) is July (90.7°F).
The month with the lowest average high temperature is January (44.2°F).
- Average low temperature in September: 62.6°F
The month with the highest average low temperature is July (69.6°F).
The coldest month (with the lowest average low temperature) is January (29.5°F).
Average pressure in September
Roslyn Hills, VA
- Average pressure in September: 30.04"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).
Average wind speed in September
Roslyn Hills, VA
- Average wind speed in September: 5.7mph
The windiest month (with the highest average wind speed) is April (7.4mph).
The calmest month (with the lowest average wind speed) is August (5.2mph).
Average humidity in September
Roslyn Hills, VA
- Average humidity in September: 73%
The month with the highest relative humidity is December (78%).
The month with the lowest relative humidity is July (68%).
Average rainfall in September
Roslyn Hills, VA
- Average rainfall in September: 1.65"
The wettest month (with the highest rainfall) is August (2.72").
The driest month (with the least rainfall) is September (1.65").
Average rainfall days in September
Roslyn Hills, VA
- Average rainfall days in September: 12.5 days
The month with the highest number of rainy days is May (16.6 days).
The month with the least rainy days is November (8.8 days).
Average snowfall in September
Roslyn Hills, VA
- Average snowfall in September: 0"
The month with the highest snowfall is February (1.77").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Roslyn Hills, VA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (3.5 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Roslyn Hills, VA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in September: 8h and 4min
The month with the most sunshine is July (Average sunshine: 10h and 36min).
The month with the least sunshine is December (Average sunshine: 5h and 12min).
Average sunshine days in September
Roslyn Hills, VA
- Average sunshine days in September: 15.8 days
The month with the most sunshine days is November (19.5 days).
The month with the least sunshine days is May (11.9 days).
Average UV index in September
Roslyn Hills, VA
- Average UV index in September: 5
The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February and December (UV index 2).
Average cloud cover in September
Roslyn Hills, VA
- Average cloud cover in September: 39
The month with the most cloud cover is March (Cloud cover 47).
The month with the least cloud cover is July (Cloud cover 31).
Average visibility in September
Roslyn Hills, 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).
Roslyn Hills, Virginia, USA
Weather forecast for your location
2. Allow the app to use your location