September weather forecastForest Grove, OR
September
Weather in September
Forest Grove welcomes the Autumn season in September, bundling up to combat the dropping temperatures. September also brings increased rainfall, signaling a transition from the dry Summer months. Despite the mild coolness, the temperatures this month are still relatively high, hovering around a maximum of 71.6°F (22°C) and a minimum of 49.8°F (9.9°C). As the month draws to a close, October continues the journey into Autumn.Temperature
With the onset of September, Forest Grove experiences a modest temperature adjustment, with the average high-temperature gently receding from a warm 79.3°F (26.3°C) in August to an agreeable 71.6°F (22°C). Forest Grove records a pronounced decline from the day's peak to an average nighttime low-temperature of 49.8°F (9.9°C) throughout September.Humidity
The average relative humidity in September is 74%.Rainfall
In Forest Grove, in September, during 11.4 rainfall days, 1.57" (40mm) of precipitation is typically accumulated. In Forest Grove, during the entire year, the rain falls for 183.5 days and collects up to 34.45" (875mm) of precipitation.Snowfall
In Forest Grove, snow does not fall in April through October.Daylight
The average length of the day in September is 12h and 31min.On the first day of the month, sunrise is at 6:34 am and sunset at 7:49 pm. On the last day of September, sunrise is at 7:10 am and sunset at 6:53 pm PDT.
Sunshine
In Forest Grove, the average sunshine in September is 8.7h.UV index
In Forest Grove, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a moderate health risk from unprotected exposure to Sun's UV rays for the ordinary person.Note: In September, a regular UV index of 4 translates into these guidelines:
Heed the precautions - It is counselled to guard against solar damage. To avoid the Sun's strongest rays, limit exposure around the mid-day period. Limit sun-induced ocular harm with sunglasses that feature UVA and UVB filtration.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Forest Grove, OR
- Average high temperature in September: 71.6°F
The warmest month (with the highest average high temperature) is August (79.3°F).
The month with the lowest average high temperature is December (43°F).
- Average low temperature in September: 49.8°F
The month with the highest average low temperature is August (53.2°F).
The coldest month (with the lowest average low temperature) is December (33.1°F).
Average pressure in September
Forest Grove, OR
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are August and September (30.01"Hg).
Average wind speed in September
Forest Grove, OR
- Average wind speed in September: 4.1mph
The windiest month (with the highest average wind speed) is March (4.9mph).
The calmest month (with the lowest average wind speed) is August (4mph).
Average humidity in September
Forest Grove, OR
- Average humidity in September: 74%
The months with the highest relative humidity are February and December (88%).
The month with the lowest relative humidity is August (69%).
Average rainfall in September
Forest Grove, OR
- Average rainfall in September: 1.57"
The wettest month (with the highest rainfall) is January (5.47").
The driest months (with the least rainfall) are July and August (0.47").
Average rainfall days in September
Forest Grove, OR
- Average rainfall days in September: 11.4 days
The month with the highest number of rainy days is March (21.4 days).
The month with the least rainy days is August (6.2 days).
Average snowfall in September
Forest Grove, OR
- Average snowfall in September: 0"
The month with the highest snowfall is February (1.54").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Forest Grove, OR
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (2.9 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
Forest Grove, 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: 8h and 42min
The month with the most sunshine is August (Average sunshine: 10h and 24min).
The months with the least sunshine are January and February (Average sunshine: 3h and 30min).
Average sunshine days in September
Forest Grove, OR
- Average sunshine days in September: 16.1 days
The month with the most sunshine days is August (22 days).
The month with the least sunshine days is March (7.6 days).
Average UV index in September
Forest Grove, OR
- Average UV index in September: 4
The months with the highest UV index are June and July (UV index 5).
The month with the lowest UV index is November (UV index 1).
Average cloud cover in September
Forest Grove, OR
- Average cloud cover in September: 39
The month with the most cloud cover is February (Cloud cover 66).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility in September
Forest Grove, OR
- 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, March, November and December (4mi).
