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 brings a slight decrease in the average high-temperature, shifting from a warm 77°F (25°C) in August to a pleasant 70°F (21.1°C). Issaquah, during the nights of September, registers a substantial plunge from the daytime high, averaging at a chilly 48.4°F (9.1°C).Humidity
The average relative humidity in September in Issaquah is 74%.Rainfall
In Issaquah, in September, it is raining for 7.8 days, with typically 0.63" (16mm) of accumulated precipitation. In Issaquah, during the entire year, the rain falls for 127.4 days and collects up to 12.52" (318mm) of precipitation.Snowfall
In Issaquah, snow does not fall in May through October.Daylight
In Issaquah, the average length of the day in September is 12h and 32min.On the first day of September, sunrise is at 6:28 am and sunset at 7:47 pm. On the last day of the month, sunrise is at 7:06 am and sunset at 6:48 pm PDT.
Sunshine
In September, the average sunshine in Issaquah, Washington, is 9.1h.UV index
The average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a moderate health risk from unprotected exposure to Sun's UV rays for the ordinary person.Note: In September, the maximum UV index of 4 suggests this advice:
Guard yourself - Avoiding sunburn is suggested. Around midday, solar radiation is most harmful; hence, exposure should be limited. To best shield against UV radiation, choose sun-safe garments and dependable sunglasses.
Frequently asked questions
What is the average September temperature in Issaquah?
What is the average humidity in September in Issaquah?
How much does it rain in Issaquah in September?
When it does not snow in Issaquah?
What is the average length of the day in September in Issaquah?
When is the sunrise / sunset in September in Issaquah?
How long on average sun shines in September in Issaquah?
How high is the UV index in September in Issaquah?
Average temperature in September
Issaquah, WA
- Average high temperature in September: 70°F
The warmest month (with the highest average high temperature) is August (77°F).
The month with the lowest average high temperature is December (42.3°F).
- Average low temperature in September: 48.4°F
The month with the highest average low temperature is August (51.4°F).
The coldest months (with the lowest average low temperature) are February and December (33.4°F).
Average pressure in September
Issaquah, 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
Issaquah, WA
- Average wind speed in September: 3.7mph
The windiest month (with the highest average wind speed) is January (5.1mph).
The calmest month (with the lowest average wind speed) is August (3.4mph).
Average humidity in September
Issaquah, WA
- Average humidity in September: 74%
The months with the highest relative humidity are January and February (85%).
The month with the lowest relative humidity is July (69%).
Average rainfall in September
Issaquah, WA
- Average rainfall in September: 0.63"
The wettest month (with the highest rainfall) is December (2.01").
The driest month (with the least rainfall) is July (0.24").
Average rainfall days in September
Issaquah, WA
- Average rainfall days in September: 7.8 days
The month with the highest number of rainy days is March (14.8 days).
The month with the least rainy days is August (4.3 days).
Average snowfall in September
Issaquah, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (0.94").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Issaquah, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (2.5 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
Issaquah, 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 30min).
- Average sunshine in September: 9h and 1min
The month with the most sunshine is August (Average sunshine: 10h and 30min).
The month with the least sunshine is December (Average sunshine: 4h and 0min).
Average sunshine days in September
Issaquah, WA
- Average sunshine days in September: 19 days
The month with the most sunshine days is August (25 days).
The month with the least sunshine days is February (12.9 days).
Average UV index in September
Issaquah, 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
Issaquah, WA
- Average cloud cover in September: 36
The months with the most cloud cover are January and December (Cloud cover 58).
The month with the least cloud cover is August (Cloud cover 27).
Average visibility in September
Issaquah, WA
- Average visibility in September: 5mi
The months with the highest visibility are July and August (6mi).
The months with the lowest visibility are January, February and December (4mi).
Issaquah, Washington, USA
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