September weather forecastPotomac, MD
September
Weather in September
September, the first month of the autumn in Potomac, is still a warm month, with temperature in the range of an average low of 60.8°F (16°C) and an average high of 78.3°F (25.7°C).Temperature
September signifies a minor drop in average high-temperature, transitioning from a moderately hot 85.5°F (29.7°C) in August to a still warm 78.3°F (25.7°C). Throughout September, Potomac experiences a low-temperature average of 60.8°F (16°C).Humidity
The average relative humidity in September is 74%.Rainfall
In Potomac, Maryland, during September, the rain falls for 14.1 days and regularly aggregates up to 2.13" (54mm) of precipitation. In Potomac, during the entire year, the rain falls for 156.5 days and collects up to 30.71" (780mm) of precipitation.Snowfall
May through October are months without snowfall.Daylight
In Potomac, the average length of the day in September is 12h and 26min.On the first day of the month, sunrise is at 6:38 am and sunset at 7:38 pm. On the last day of September, sunrise is at 7:04 am and sunset at 6:52 pm EDT.
Sunshine
In September, the average sunshine is 8.9h.UV index
The average daily maximum UV index in September in Potomac is 5. A UV Index reading of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for ordinary individuals.Note: An average maximum UV index of 5 in September leads to these recommendations:
Exercise caution. The susceptibility of light skin individuals to burns is less than 30 minutes. Direct exposure to the Sun's intense radiation around midday should be avoided for health reasons. Opt for tightly woven and loose clothing to enhance protection from the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Potomac, MD
- Average high temperature in September: 78.3°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 (39.4°F).
- Average low temperature in September: 60.8°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 (26.4°F).
Average pressure in September
Potomac, MD
- 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).
Average wind speed in September
Potomac, MD
- Average wind speed in September: 5.5mph
The windiest month (with the highest average wind speed) is March (7.8mph).
The calmest month (with the lowest average wind speed) is August (4.9mph).
Average humidity in September
Potomac, MD
- Average humidity in September: 74%
The months with the highest relative humidity are October and December (76%).
The month with the lowest relative humidity is July (69%).
Average rainfall in September
Potomac, MD
- Average rainfall in September: 2.13"
The wettest month (with the highest rainfall) is August (3.86").
The driest month (with the least rainfall) is February (1.93").
Average rainfall days in September
Potomac, MD
- Average rainfall days in September: 14.1 days
The month with the highest number of rainy days is August (17.3 days).
The month with the least rainy days is January (8.1 days).
Average snowfall in September
Potomac, MD
- Average snowfall in September: 0"
The month with the highest snowfall is March (3.03").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Potomac, MD
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (4.8 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
Potomac, MD
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in September: 8h and 54min
The month with the most sunshine is July (Average sunshine: 10h and 48min).
The month with the least sunshine is February (Average sunshine: 5h and 0min).
Average sunshine days in September
Potomac, MD
- Average sunshine days in September: 14.5 days
The month with the most sunshine days is November (19.9 days).
The month with the least sunshine days is May (11.7 days).
Average UV index in September
Potomac, MD
- 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).
Average cloud cover in September
Potomac, MD
- Average cloud cover in September: 37
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
Potomac, MD
- 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).
