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
September's arrival comes with a decrease in the average high-temperature, moving from a moderately hot 75.4°F (24.1°C) in August to a refreshing 64.6°F (18.1°C). Roslyn anticipates a stark contrast in temperature during September nights, with an average low of 42.3°F (5.7°C).Humidity
In Roslyn, the average relative humidity in September is 68%.Rainfall
In Roslyn, Washington, in September, during 10.7 rainfall days, 1.1" (28mm) of precipitation is typically accumulated. Throughout the year, there are 161.2 rainfall days, and 28.46" (723mm) of precipitation is accumulated.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 0.2" (5mm) of snow. Throughout the year, there are 69.9 snowfall days, and 60.24" (1530mm) of snow is accumulated.Daylight
In Roslyn, the average length of the day in September is 12h and 32min.On the first day of the month, sunrise is at 6:24 am and sunset at 7:43 pm. On the last day of September, sunrise is at 7:02 am and sunset at 6:44 pm PDT.
Sunshine
The average sunshine in September is 10.2h.UV index
In Roslyn, the average daily maximum UV index in September is 3. A UV Index estimate of 3 to 5 represents a moderate threat to health from unsafe exposure to UV radiation for average individuals.Note: A daily maximum UV index of 3 in September translates into the following instructions:
Be vigilant - Preventing sunburn is recommended. Solar radiation peaks around mid-day, so it's wise to limit exposure to the Sun at this time. Counter UV radiation's ill effects with clothing designed for sun safety and UV-resistant eyewear. Be aware! The reflective nature of snow can magnify the Sun's UV radiation almost twofold.
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 much does it rain in September?
When does it start snowing?
How many hours of daylight does Roslyn have in September?
When are sunrise and sunset in September?
How many hours of sunshine does Roslyn have in September?
What is the UV index reading in September in Roslyn?
Average temperature in September
Roslyn, WA
- Average high temperature in September: 64.6°F
The warmest month (with the highest average high temperature) is August (75.4°F).
The month with the lowest average high temperature is December (29.7°F).
- Average low temperature in September: 42.3°F
The month with the highest average low temperature is August (47.8°F).
The coldest month (with the lowest average low temperature) is December (18.3°F).
Average pressure in September
Roslyn, WA
- Average pressure in September: 29.98"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is August (29.96"Hg).
Average wind speed in September
Roslyn, WA
- Average wind speed in September: 5.3mph
The windiest month (with the highest average wind speed) is June (6.7mph).
The calmest month (with the lowest average wind speed) is December (4.2mph).
Average humidity in September
Roslyn, WA
- Average humidity in September: 68%
The months with the highest relative humidity are January and February (92%).
The months with the lowest relative humidity are July and August (60%).
Average rainfall in September
Roslyn, WA
- Average rainfall in September: 1.1"
The wettest month (with the highest rainfall) is January (4.41").
The driest month (with the least rainfall) is July (0.39").
Average rainfall days in September
Roslyn, WA
- Average rainfall days in September: 10.7 days
The months with the highest number of rainy days are March and April (18.3 days).
The month with the least rainy days is August (5.5 days).
Average snowfall in September
Roslyn, WA
- Average snowfall in September: 0.2"
The month with the highest snowfall is January (16.3").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Roslyn, WA
- Average snowfall days in September: 0.2 days
The month with the highest number of snowfall days is December (15.1 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Roslyn, WA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 36min).
- Average sunshine in September: 10h and 1min
The month with the most sunshine is August (Average sunshine: 11h and 54min).
The month with the least sunshine is January (Average sunshine: 3h and 24min).
Average sunshine days in September
Roslyn, WA
- Average sunshine days in September: 16.3 days
The month with the most sunshine days is August (22.8 days).
The month with the least sunshine days is February (6.8 days).
Average UV index in September
Roslyn, WA
- Average UV index in September: 3
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 1).
Average cloud cover in September
Roslyn, WA
- Average cloud cover in September: 30
The month with the most cloud cover is January (Cloud cover 63).
The months with the least cloud cover are July and August (Cloud cover 18).
Average visibility in September
Roslyn, WA
- Average visibility in September: 6mi
The months with the highest visibility are May, June, July, August and September (6mi).
The month with the lowest visibility is January (3mi).
Roslyn, Washington, USA
Weather forecast for your location
2. Allow the app to use your location