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 onset introduces a mild reduction in the average high-temperature, from an agreeable 72.7°F (22.6°C) in August to a refreshing 67.1°F (19.5°C). An average low-temperature of 51.4°F (10.8°C) is anticipated throughout the nights during September.Humidity
The average relative humidity in September is 77%.Rainfall
In Mill Creek, during September, the rain falls for 11.3 days and regularly aggregates up to 1.5" (38mm) of precipitation. Throughout the year, there are 173.1 rainfall days, and 26.02" (661mm) of precipitation is accumulated.Snowfall
May through October are months without snowfall.Daylight
In September, the average length of the day 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
In September, the average sunshine is 9.4h.UV index
In Mill Creek, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a medium vulnerability from unprotected exposure to Sun's UV rays for average individuals.Note: The maximum daily UV index, 4 in September, converts into the following recommendations:
Guard yourself - Avoiding sunburn is suggested. Solar radiation is at its peak intensity during midday, so it's advisable to stay indoors or in the shade. For holistic sun protection encompassing the eyes, ears, face, and neck, a wide-brim hat is key.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the average humidity in September?
How many days does it rain in September?
When it does not snow?
How many hours of daylight does Mill Creek have in September?
When are sunrise and sunset in September?
How long on average sun shines in September?
What is the UV index intensity in September?
Average temperature in September
Mill Creek, WA
- Average high temperature in September: 67.1°F
The warmest month (with the highest average high temperature) is August (72.7°F).
The month with the lowest average high temperature is December (42.6°F).
- Average low temperature in September: 51.4°F
The month with the highest average low temperature is August (54°F).
The coldest month (with the lowest average low temperature) is December (35.4°F).
Average pressure in September
Mill Creek, 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
Mill Creek, WA
- Average wind speed in September: 4.2mph
The windiest month (with the highest average wind speed) is November (6.2mph).
The calmest month (with the lowest average wind speed) is August (3.6mph).
Average humidity in September
Mill Creek, WA
- Average humidity in September: 77%
The months with the highest relative humidity are February and December (84%).
The month with the lowest relative humidity is July (72%).
Average rainfall in September
Mill Creek, WA
- Average rainfall in September: 1.5"
The wettest month (with the highest rainfall) is December (3.54").
The driest month (with the least rainfall) is July (0.43").
Average rainfall days in September
Mill Creek, WA
- Average rainfall days in September: 11.3 days
The month with the highest number of rainy days is March (19.8 days).
The month with the least rainy days is August (6.3 days).
Average snowfall in September
Mill Creek, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (4.61").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Mill Creek, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (5.2 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
Mill Creek, WA
- Average daylight in September: 12h and 4min
The month with the longest days is June (Average daylight: 16h and 0min).
The month with the shortest days is December (Average daylight: 8h and 30min).
- Average sunshine in September: 9h and 2min
The month with the most sunshine is August (Average sunshine: 10h and 42min).
The month with the least sunshine is January (Average sunshine: 4h and 24min).
Average sunshine days in September
Mill Creek, WA
- Average sunshine days in September: 16.5 days
The month with the most sunshine days is August (22.6 days).
The month with the least sunshine days is November (9.1 days).
Average UV index in September
Mill Creek, 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
Mill Creek, WA
- Average cloud cover in September: 32
The month with the most cloud cover is December (Cloud cover 54).
The month with the least cloud cover is August (Cloud cover 25).
Average visibility in September
Mill Creek, 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).
Mill Creek, Washington, USA
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