September weather forecastMountlake Terrace, WA
September
Weather in September
The first month of the autumn, September, is still a comfortable month in Mountlake Terrace, Washington, with an average temperature fluctuating between 67.6°F (19.8°C) and 51.6°F (10.9°C).Temperature
September brings a slight decrease in the average high-temperature, shifting from a moderately hot 73.9°F (23.3°C) in August to an enjoyable 67.6°F (19.8°C). Mountlake Terrace reports a consistent average low-temperature of 51.6°F (10.9°C) throughout September nights.Humidity
In Mountlake Terrace, the average relative humidity in September is 76%.Rainfall
In Mountlake Terrace, during September, the rain falls for 11.9 days and regularly aggregates up to 1.42" (36mm) of precipitation. In Mountlake Terrace, during the entire year, the rain falls for 173 days and collects up to 25" (635mm) of precipitation.Snowfall
In Mountlake Terrace, snow does not fall in May through October.Daylight
The average length of the day in September is 12h and 33min.On the first day of September, sunrise is at 6:28 am and sunset at 7:49 pm. On the last day of the month, sunrise is at 7:08 am and sunset at 6:49 pm PDT.
Sunshine
In Mountlake Terrace, the average sunshine in September is 9.5h.UV index
In Mountlake Terrace, the average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a moderate threat to health from unsafe exposure to UV radiation for the ordinary person.Note: In September, the UV index of 4 transforms into the following advice:
Undertake protective steps - Recommendations to avoid sunburn are issued. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. Combat UV radiation's detrimental effects with sun-safe clothing and UV-blocking eyewear.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Mountlake Terrace, WA
- Average high temperature in September: 67.6°F
The warmest month (with the highest average high temperature) is August (73.9°F).
The month with the lowest average high temperature is December (43.3°F).
- Average low temperature in September: 51.6°F
The month with the highest average low temperature is August (54.1°F).
The coldest month (with the lowest average low temperature) is December (35.8°F).
Average pressure in September
Mountlake Terrace, 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
Mountlake Terrace, WA
- Average wind speed in September: 4mph
The windiest month (with the highest average wind speed) is November (5.9mph).
The calmest month (with the lowest average wind speed) is August (3.5mph).
Average humidity in September
Mountlake Terrace, WA
- Average humidity in September: 76%
The months with the highest relative humidity are January, February and December (84%).
The month with the lowest relative humidity is July (72%).
Average rainfall in September
Mountlake Terrace, WA
- Average rainfall in September: 1.42"
The wettest month (with the highest rainfall) is December (3.5").
The driest month (with the least rainfall) is July (0.39").
Average rainfall days in September
Mountlake Terrace, WA
- Average rainfall days in September: 11.9 days
The month with the highest number of rainy days is March (19.8 days).
The month with the least rainy days is August (6.8 days).
Average snowfall in September
Mountlake Terrace, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (3.58").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Mountlake Terrace, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (4.7 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
Mountlake Terrace, 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 30min
The month with the most sunshine is August (Average sunshine: 10h and 48min).
The month with the least sunshine is January (Average sunshine: 4h and 30min).
Average sunshine days in September
Mountlake Terrace, WA
- Average sunshine days in September: 15.9 days
The month with the most sunshine days is August (22.5 days).
The month with the least sunshine days is November (9.2 days).
Average UV index in September
Mountlake Terrace, WA
- Average UV index in September: 4
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
Mountlake Terrace, WA
- Average cloud cover in September: 32
The months with the most cloud cover are January and December (Cloud cover 53).
The month with the least cloud cover is August (Cloud cover 25).
Average visibility in September
Mountlake Terrace, WA
- Average visibility in September: 6mi
The months with the highest visibility are February, March, April, May, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is January (5mi).
