September weather forecastWilsonville, OR
September
Weather in September
September marks the transition from summer back to fall in Wilsonville, Oregon. Additional hours of sunlight linger, providing ample opportunity for sightseeing. There’s a pronounced drop in temperature from August's peak, with average high temperature falling to 73.2°F (22.9°C). The days gradually shorten and the climate becomes more crisp as September progresses. Yet, the relatively dry conditions and warmer temperatures make it a celebrated time to be outdoors.Temperature
The arrival of September is marked by a minor reduction in average high-temperature, sliding from a warm 81°F (27.2°C) in August to a pleasant 73.2°F (22.9°C). In Wilsonville, a significant divergence from daytime highs is recorded, with average lows of 50.9°F (10.5°C) during September nights.Humidity
In September, the average relative humidity is 70%.Rainfall
In Wilsonville, during September, the rain falls for 9.9 days and regularly aggregates up to 1.54" (39mm) of precipitation. In Wilsonville, during the entire year, the rain falls for 173.8 days and collects up to 29.96" (761mm) of precipitation.Snowfall
In Wilsonville, snow does not fall in April through October.Daylight
In Wilsonville, the average length of the day in September is 12h and 31min.On the first day of the month, sunrise is at 6:33 am and sunset at 7:47 pm. On the last day of September, sunrise is at 7:09 am and sunset at 6:52 pm PDT.
Sunshine
In Wilsonville, the average sunshine in September is 9.4h.UV index
In September, the average daily maximum UV index is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from unprotected exposure to Sun's UV rays for the ordinary person.Note: In September, the UV index of 4 transforms into the following advice:
Take necessary precautions - Defending against sun damage is advocated. The intensity of the Sun's UV radiation during midday suggests reducing time spent outdoors. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Wilsonville, OR
- Average high temperature in September: 73.2°F
The warmest month (with the highest average high temperature) is August (81°F).
The month with the lowest average high temperature is December (44.2°F).
- Average low temperature in September: 50.9°F
The month with the highest average low temperature is August (54°F).
The coldest month (with the lowest average low temperature) is December (34.3°F).
Average pressure in September
Wilsonville, OR
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.12"Hg).
The months with the lowest atmospheric pressure are August and September (30.01"Hg).
Average wind speed in September
Wilsonville, OR
- Average wind speed in September: 4mph
The windiest months (with the highest average wind speed) are January and February (5.5mph).
The calmest month (with the lowest average wind speed) is August (3.8mph).
Average humidity in September
Wilsonville, OR
- Average humidity in September: 70%
The months with the highest relative humidity are January, February and December (85%).
The month with the lowest relative humidity is August (65%).
Average rainfall in September
Wilsonville, OR
- Average rainfall in September: 1.54"
The wettest month (with the highest rainfall) is December (4.49").
The driest months (with the least rainfall) are July and August (0.31").
Average rainfall days in September
Wilsonville, OR
- Average rainfall days in September: 9.9 days
The month with the highest number of rainy days is March (20.9 days).
The months with the least rainy days are July and August (4.4 days).
Average snowfall in September
Wilsonville, OR
- Average snowfall in September: 0"
The month with the highest snowfall is February (1.26").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Wilsonville, OR
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (2.1 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Wilsonville, OR
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 36min).
The month with the shortest days is December (Average daylight: 8h and 48min).
- Average sunshine in September: 9h and 24min
The month with the most sunshine is August (Average sunshine: 11h and 6min).
The month with the least sunshine is February (Average sunshine: 4h and 12min).
Average sunshine days in September
Wilsonville, OR
- Average sunshine days in September: 18.1 days
The month with the most sunshine days is July (25 days).
The month with the least sunshine days is March (8.3 days).
Average UV index in September
Wilsonville, OR
- 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
Wilsonville, OR
- Average cloud cover in September: 31
The month with the most cloud cover is February (Cloud cover 58).
The month with the least cloud cover is August (Cloud cover 21).
Average visibility in September
Wilsonville, OR
- Average visibility in September: 6mi
The months with the highest visibility are July, August and September (6mi).
The months with the lowest visibility are January, February, March, April, May, June, October, November and December (5mi).
