September weather forecastWest Lake Sammamish, WA
September
Weather in September
September, the first month of the autumn in West Lake Sammamish, is still a pleasant month, with temperature in the range of an average low of 48.9°F (9.4°C) and an average high of 69.8°F (21°C).Temperature
The beginning of September brings a minor change in the average high-temperature, shifting from a moderately hot 76.5°F (24.7°C) in August to an agreeable 69.8°F (21°C). Throughout September, West Lake Sammamish records an average temperature of 48.9°F (9.4°C) at night.Humidity
In September, the average relative humidity is 75%.Rainfall
In September, in West Lake Sammamish, the rain falls for 10.1 days. Throughout September, 1.06" (27mm) of precipitation is accumulated. Throughout the year, there are 136.7 rainfall days, and 13.39" (340mm) of precipitation is accumulated.Snowfall
May through October are months without snowfall.Daylight
The average length of the day in September in West Lake Sammamish is 12h and 33min.On the first day of the month, sunrise is at 6:28 am and sunset at 7:48 pm. On the last day of September, sunrise is at 7:07 am and sunset at 6:49 pm PDT.
Sunshine
The average sunshine in September is 9.2h.UV index
The average daily maximum UV index in September is 3. A UV Index estimate of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV rays for ordinary individuals.Note: In September, the maximum UV index of 3 translates into these guidelines:
Stay alert. Light-skinned people could suffer burns in less than 30 minutes. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. A wide-brim hat offers excellent sun protection for the eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Be advised! The UV radiation from the Sun can be almost doubled due to the reflective properties of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
West Lake Sammamish, WA
- Average high temperature in September: 69.8°F
The warmest month (with the highest average high temperature) is August (76.5°F).
The month with the lowest average high temperature is December (42.3°F).
- Average low temperature in September: 48.9°F
The month with the highest average low temperature is August (52.2°F).
The coldest month (with the lowest average low temperature) is December (33.6°F).
Average pressure in September
West Lake Sammamish, WA
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).
Average wind speed in September
West Lake Sammamish, WA
- Average wind speed in September: 3.7mph
The windiest month (with the highest average wind speed) is January (5mph).
The calmest month (with the lowest average wind speed) is August (3.4mph).
Average humidity in September
West Lake Sammamish, WA
- Average humidity in September: 75%
The months with the highest relative humidity are January, February and December (85%).
The month with the lowest relative humidity is July (70%).
Average rainfall in September
West Lake Sammamish, WA
- Average rainfall in September: 1.06"
The wettest month (with the highest rainfall) is December (1.85").
The driest months (with the least rainfall) are July and August (0.35").
Average rainfall days in September
West Lake Sammamish, WA
- Average rainfall days in September: 10.1 days
The month with the highest number of rainy days is March (14.8 days).
The month with the least rainy days is August (5.2 days).
Average snowfall in September
West Lake Sammamish, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (1.38").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
West Lake Sammamish, WA
- Average snowfall days in September: 0.1 days
The month with the highest number of snowfall days is February (3.2 days).
The months with the least snowfall days are May, June, July, August and October (0 days).
Average daylight in September /
Average sunshine in September
West Lake Sammamish, WA
- Average daylight in September: 12h and 30min
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 30min).
- Average sunshine in September: 9h and 12min
The month with the most sunshine is August (Average sunshine: 10h and 42min).
The months with the least sunshine are January and December (Average sunshine: 4h and 12min).
Average sunshine days in September
West Lake Sammamish, WA
- Average sunshine days in September: 17.7 days
The month with the most sunshine days is August (24 days).
The month with the least sunshine days is November (13.5 days).
Average UV index in September
West Lake Sammamish, WA
- Average UV index in September: 3
The months with the highest UV index are June and 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
West Lake Sammamish, WA
- Average cloud cover in September: 34
The month with the most cloud cover is December (Cloud cover 57).
The month with the least cloud cover is August (Cloud cover 26).
Average visibility in September
West Lake Sammamish, WA
- Average visibility in September: 6mi
The months with the highest visibility are June, July, August and September (6mi).
The months with the lowest visibility are January, February, March, April, May, October, November and December (5mi).
