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
Arrival of September comes with a reduction in the average high-temperature, falling from a moderately hot 81°F (27.2°C) in August to an agreeable 71.2°F (21.8°C). A considerable shift from the daytime highs is observed during September nights, with an average low of 44.2°F (6.8°C).Humidity
In September, the average relative humidity is 51%.Rainfall
In Mount Vernon, during September, the rain falls for 6.6 days and regularly aggregates up to 0.55" (14mm) of precipitation. In Mount Vernon, during the entire year, the rain falls for 127.7 days and collects up to 17.09" (434mm) of precipitation.Snowfall
Months with snowfall are January through May, September through December. September is the first month it typically snows. Throughout September, in the average 0.2 snowfall days, it receives 0.08" (2mm) of snow. In Mount Vernon, during the entire year, snow falls for 62.5 days and aggregates up to 39.17" (995mm) of snow.Daylight
In September, the average length of the day is 12h and 30min.On the first day of September, sunrise is at 6:20 am and sunset at 7:32 pm. On the last day of the month, sunrise is at 6:54 am and sunset at 6:38 pm PDT.
Sunshine
In September, the average sunshine is 10.7h.UV index
In September, the average daily maximum UV index is 3. A UV Index reading of 3 to 5 represents a moderate health risk from exposure to the Sun's UV radiation for ordinary individuals.Note: In September, the maximum UV index of 3 transforms into these recommendations:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. For a sun-safe wardrobe, go for clothes that are tightly woven and generously sized. Take precaution! The reflection from snow can almost double the UV radiation of the Sun.
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?
How many days does it rain in September?
When does it start to snow?
How many hours of daylight does Mount Vernon have in September?
When are sunrise and sunset in September?
How many hours of sunshine does Mount Vernon have in September?
What is the UV index reading in September?
Average temperature in September
Mount Vernon, OR
- Average high temperature in September: 71.2°F
The warmest month (with the highest average high temperature) is July (81.7°F).
The month with the lowest average high temperature is December (33.4°F).
- Average low temperature in September: 44.2°F
The month with the highest average low temperature is August (49.6°F).
The coldest month (with the lowest average low temperature) is December (19.6°F).
Average pressure in September
Mount Vernon, OR
- Average pressure in September: 29.97"Hg
The month with the highest atmospheric pressure is January (30.22"Hg).
The month with the lowest atmospheric pressure is August (29.93"Hg).
Average wind speed in September
Mount Vernon, OR
- Average wind speed in September: 5mph
The windiest month (with the highest average wind speed) is April (6.2mph).
The calmest months (with the lowest average wind speed) are August and September (5mph).
Average humidity in September
Mount Vernon, OR
- Average humidity in September: 51%
The month with the highest relative humidity is February (85%).
The month with the lowest relative humidity is August (42%).
Average rainfall in September
Mount Vernon, OR
- Average rainfall in September: 0.55"
The wettest month (with the highest rainfall) is February (2.28").
The driest month (with the least rainfall) is July (0.24").
Average rainfall days in September
Mount Vernon, OR
- Average rainfall days in September: 6.6 days
The month with the highest number of rainy days is March (17.3 days).
The month with the least rainy days is August (3.3 days).
Average snowfall in September
Mount Vernon, OR
- Average snowfall in September: 0.08"
The month with the highest snowfall is February (10.31").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Mount Vernon, OR
- Average snowfall days in September: 0.2 days
The month with the highest number of snowfall days is December (14.5 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Mount Vernon, OR
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 30min).
The month with the shortest days is December (Average daylight: 8h and 54min).
- Average sunshine in September: 10h and 4min
The month with the most sunshine is August (Average sunshine: 12h and 6min).
The months with the least sunshine are January and February (Average sunshine: 5h and 12min).
Average sunshine days in September
Mount Vernon, OR
- Average sunshine days in September: 21.8 days
The month with the most sunshine days is July (24.9 days).
The month with the least sunshine days is February (9 days).
Average UV index in September
Mount Vernon, OR
- Average UV index in September: 3
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, March, October, November and December (UV index 2).
Average cloud cover in September
Mount Vernon, OR
- Average cloud cover in September: 17
The month with the most cloud cover is February (Cloud cover 49).
The months with the least cloud cover are July and August (Cloud cover 9).
Average visibility in September
Mount Vernon, OR
- Average visibility in September: 6mi
The months with the highest visibility are April, May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February and December (4mi).
Mount Vernon, Oregon, USA
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