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 arrival of September coincides with an average high-temperature of a refreshing 64°F (17.8°C), indicating a minimal shift from August's 68.4°F (20.2°C). Throughout September, Mount Vernon's nights cool down to an average of 51.4°F (10.8°C).Humidity
In Mount Vernon, the average relative humidity in September is 79%.Rainfall
In Mount Vernon, in September, during 12.1 rainfall days, 2.24" (57mm) of precipitation is typically accumulated. Throughout the year, there are 185.2 rainfall days, and 34.72" (882mm) of precipitation is accumulated.Snowfall
May through October are months without snowfall.Daylight
The average length of the day in September is 12h and 34min.On the first day of the month, sunrise is at 6:28 am and sunset at 7:50 pm. On the last day of September, sunrise is at 7:08 am and sunset at 6:49 pm PDT.
Sunshine
In Mount Vernon, the average sunshine in September is 9h.UV index
In Mount Vernon, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a medium vulnerability from exposure to the Sun's UV rays for ordinary individuals.Note: The UV index of 4 in September translates into these instructions:
Exercise care. People with light skin might get burns in fewer than 30 minutes. To avoid the Sun's strongest rays, limit exposure around the mid-day period. 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
What are September temperatures?
What is the average humidity in September?
How much does it rain in September?
When it does not snow?
How many hours of daylight does Mount Vernon have in September?
When is the sunrise / sunset in September?
How long on average sun shines in September?
What is the UV index reading in September?
Average temperature in September
Mount Vernon, WA
- Average high temperature in September: 64°F
The warmest months (with the highest average high temperature) are July and August (68.4°F).
The month with the lowest average high temperature is December (42.6°F).
- Average low temperature in September: 51.4°F
The month with the highest average low temperature is August (54.1°F).
The coldest month (with the lowest average low temperature) is February (36.1°F).
Average pressure in September
Mount Vernon, WA
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.09"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).
Average wind speed in September
Mount Vernon, WA
- Average wind speed in September: 4.5mph
The windiest month (with the highest average wind speed) is November (7.5mph).
The calmest month (with the lowest average wind speed) is August (3.7mph).
Average humidity in September
Mount Vernon, WA
- Average humidity in September: 79%
The months with the highest relative humidity are January and February (83%).
The month with the lowest relative humidity is July (75%).
Average rainfall in September
Mount Vernon, WA
- Average rainfall in September: 2.24"
The wettest month (with the highest rainfall) is November (4.96").
The driest month (with the least rainfall) is July (0.63").
Average rainfall days in September
Mount Vernon, WA
- Average rainfall days in September: 12.1 days
The month with the highest number of rainy days is March (20.8 days).
The month with the least rainy days is August (7.2 days).
Average snowfall in September
Mount Vernon, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (3.54").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Mount Vernon, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (3.6 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
Mount Vernon, WA
- Average daylight in September: 12h and 4min
The month with the longest days is June (Average daylight: 16h and 0min).
The month with the shortest days is December (Average daylight: 8h and 24min).
- Average sunshine in September: 9h and 0min
The months with the most sunshine are July and August (Average sunshine: 10h and 24min).
The month with the least sunshine is December (Average sunshine: 3h and 54min).
Average sunshine days in September
Mount Vernon, WA
- Average sunshine days in September: 16.3 days
The month with the most sunshine days is August (22.3 days).
The month with the least sunshine days is November (8.1 days).
Average UV index in September
Mount Vernon, WA
- Average UV index in September: 4
The month with the highest UV index is July (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Mount Vernon, WA
- Average cloud cover in September: 34
The month with the most cloud cover is December (Cloud cover 59).
The month with the least cloud cover is August (Cloud cover 26).
Average visibility in September
Mount Vernon, WA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Mount Vernon, Washington, USA
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