September weather forecastLake Oswego, OR
September
Weather in September
The city of Lake Oswego eases into the welcoming arms of the fall season in September with marked cooling in the average temperature high to 74.1°F (23.4°C). After two consecutive scorching months, the weather becomes a little more lenient, paving the way to soothing conditions. The frequency of rainfall increases, offering an atmospheric breather from the exhaustive dry phases of the summer. As the colorful transformation of the foliage begins to become noticeable, residents are treated to the spectacle of fall leaves against the backdrop of pleasant weather.Temperature
September ushers in a minor alteration in Lake Oswego's climate, with the average high-temperature moving from August's 81.7°F (27.6°C) to a still moderately hot 74.1°F (23.4°C). Lake Oswego anticipates a considerable drop in temperature at night in September, with an average low of 51.1°F (10.6°C).Humidity
In September, the average relative humidity is 69%.Rainfall
In Lake Oswego, in September, it is raining for 10.4 days, with typically 1.69" (43mm) of accumulated precipitation. Throughout the year, there are 172.2 rainfall days, and 31.3" (795mm) of precipitation is accumulated.Snowfall
In Lake Oswego, snow does not fall in April through October.Daylight
In Lake Oswego, the average length of the day in September is 12h and 31min.On the first day of September, sunrise is at 6:33 am and sunset at 7:47 pm. On the last day of the month, sunrise is at 7:08 am and sunset at 6:52 pm PDT.
Sunshine
In September, the average sunshine is 9.3h.UV index
The average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from exposure to the Sun's UV rays for average individuals.Note: A daily high UV index of 4 in September leads to these guidelines:
Take heed. Individuals of lighter complexion can be burned in less than half an hour. Limiting sun exposure during midday hours helps in reducing the harmful effects of UV radiation. A hat with a broad brim is indispensable, filtering out up to half of UV rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Lake Oswego, OR
- Average high temperature in September: 74.1°F
The warmest month (with the highest average high temperature) is August (81.7°F).
The month with the lowest average high temperature is December (44.4°F).
- Average low temperature in September: 51.1°F
The month with the highest average low temperature is August (54.5°F).
The coldest month (with the lowest average low temperature) is December (34.7°F).
Average pressure in September
Lake Oswego, OR
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.12"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).
Average wind speed in September
Lake Oswego, OR
- Average wind speed in September: 3.9mph
The windiest month (with the highest average wind speed) is January (6mph).
The calmest month (with the lowest average wind speed) is August (3.7mph).
Average humidity in September
Lake Oswego, OR
- Average humidity in September: 69%
The month with the highest relative humidity is February (84%).
The month with the lowest relative humidity is August (63%).
Average rainfall in September
Lake Oswego, OR
- Average rainfall in September: 1.69"
The wettest month (with the highest rainfall) is December (4.57").
The driest month (with the least rainfall) is July (0.31").
Average rainfall days in September
Lake Oswego, OR
- Average rainfall days in September: 10.4 days
The month with the highest number of rainy days is March (20.4 days).
The month with the least rainy days is July (4.8 days).
Average snowfall in September
Lake Oswego, OR
- Average snowfall in September: 0"
The month with the highest snowfall is March (1.46").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Lake Oswego, OR
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (2.3 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
Lake Oswego, 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 18min
The month with the most sunshine is August (Average sunshine: 11h and 0min).
The month with the least sunshine is February (Average sunshine: 4h and 12min).
Average sunshine days in September
Lake Oswego, OR
- Average sunshine days in September: 17.5 days
The month with the most sunshine days is July (23.9 days).
The month with the least sunshine days is February (8.3 days).
Average UV index in September
Lake Oswego, 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
Lake Oswego, OR
- Average cloud cover in September: 33
The month with the most cloud cover is February (Cloud cover 57).
The month with the least cloud cover is August (Cloud cover 22).
Average visibility in September
Lake Oswego, OR
- Average visibility in September: 6mi
The months with the highest visibility are July, August, September and October (6mi).
The months with the lowest visibility are January, February, March, April, May, June, November and December (5mi).
