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
With the commencement of September, Rockville records a moderate temperature decline, with the average high easing from August's tropical 88.3°F (31.3°C) to a warm 81.3°F (27.4°C). During September, Rockville experiences a consistent low-temperature average of 62.6°F (17°C).Heat index
For most parts of September, the heat index is computed to be a tropical 86°F (30°C). Continuous exposure and activity could induce a sense of tiredness and subsequently, heat cramps.Understand that the heat index values take into account shaded locations and mild winds. Direct sunlight might lead to a heat index increase by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'real feel', represents the fusion of temperature and moisture in the air to suggest how warm it feels. One's weather perception can be influenced by a range of factors including metabolic differences, being pregnant, and their level of physical activity. Remember, direct sunlight exposure can heighten the heat impact and might increase the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for babies and toddlers. Typically, young kids are at a higher risk than adults since they sweat less. Also, the larger skin surface in proportion to their small bodies and the heightened heat production due to their active nature adds to their vulnerability.
Humidity
In September, the average relative humidity is 73%.Rainfall
The month with the least rainfall is September, when the rain falls for 12.5 days and typically collects 1.65" (42mm) of precipitation.Snowfall
May through October are months without snowfall.Daylight
In September, the average length of the day is 12h and 25min.On the first day of September, sunrise is at 6:41 am and sunset at 7:39 pm. On the last day of the month, sunrise is at 7:06 am and sunset at 6:54 pm EDT.
Sunshine
In Rockville, the average sunshine in September is 8.7h.UV index
In September, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a medium vulnerability from unsafe exposure to UV radiation for average individuals.Note: The maximum daily UV index of 5 during September translates into the following directions:
Make use of precautions - It is urged to ward off sun damage. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. During bright days, sunglasses that offer UVA and UVB defense are recommended.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the average humidity in September?
What is the driest month in Rockville?
How much does it rain in Rockville in September?
When it does not snow?
What is the average length of the day in September?
What time are sunrise and sunset in September?
How many hours of sunshine does Rockville have in September?
What is the UV index reading in September?
Average temperature in September
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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
Rockville, 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).
Rockville, Virginia, USA
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