September weather forecastRenton, WA
September
Weather in September
As Renton strides into September, there is a sensed arrival of autumn marking a gentle close to summer. Average temperatures register a drop compared to August's peaks, hinting at the forthcoming cooler weather approaching. The retreat of summer also accompanies a slight rise in cloud cover, leading to shorter sunlight hours. However, conditions remain predominantly dry despite an increase in rainfall. September’s moderate wind speeds contribute to an upbeat autumn vibe, rendering it a delightful month to relish Renton's natural beauty and more temperate climate.Temperature
With the arrival of September, Renton experiences a modest decline in average high-temperatures, transitioning from a moderately hot 77.4°F (25.2°C) in August to an agreeable 70.3°F (21.3°C). Renton's nighttime temperature in September falls to an average of 50°F (10°C).Humidity
The average relative humidity in September is 73%.Rainfall
In Renton, in September, during 5.9 rainfall days, 0.31" (8mm) of precipitation is typically accumulated. In Renton, during the entire year, the rain falls for 100.6 days and collects up to 7.6" (193mm) of precipitation.Snowfall
In Renton, snow does not fall in April through October.Daylight
In Renton, Washington, 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 7:48 pm. On the last day of the month, sunrise is at 7:07 am and sunset at 6:49 pm PDT.
Sunshine
In September, the average sunshine is 9.1h.UV index
The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to UV radiation for the ordinary person.Note: A maximum UV index of 4 in September translates into the following recommendations:
Ensure safety - Imperative it is to shield skin and eyes from damage. UV radiation from the Sun is most dangerous during midday; take precautions and seek shade. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Renton, WA
- Average high temperature in September: 70.3°F
The warmest months (with the highest average high temperature) are July and August (77.4°F).
The month with the lowest average high temperature is December (43.3°F).
- Average low temperature in September: 50°F
The month with the highest average low temperature is August (53.6°F).
The coldest month (with the lowest average low temperature) is December (34.2°F).
Average pressure in September
Renton, 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
Renton, WA
- Average wind speed in September: 3.9mph
The windiest month (with the highest average wind speed) is March (5.2mph).
The calmest month (with the lowest average wind speed) is August (3.6mph).
Average humidity in September
Renton, WA
- Average humidity in September: 73%
The months with the highest relative humidity are January and December (85%).
The months with the lowest relative humidity are July and August (68%).
Average rainfall in September
Renton, WA
- Average rainfall in September: 0.31"
The wettest month (with the highest rainfall) is December (1.34").
The driest month (with the least rainfall) is July (0.12").
Average rainfall days in September
Renton, WA
- Average rainfall days in September: 5.9 days
The month with the highest number of rainy days is March (11.9 days).
The month with the least rainy days is August (3 days).
Average snowfall in September
Renton, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (0.63").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Renton, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (1.7 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
Renton, 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 6min
The month with the most sunshine is August (Average sunshine: 10h and 36min).
The months with the least sunshine are January and December (Average sunshine: 4h and 6min).
Average sunshine days in September
Renton, WA
- Average sunshine days in September: 22.1 days
The month with the most sunshine days is August (25.8 days).
The month with the least sunshine days is February (15.5 days).
Average UV index in September
Renton, WA
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Renton, WA
- Average cloud cover in September: 35
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
Renton, 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).
