September weather forecastRiley, OR
September
Weather in September
The first month of the autumn, September, is still a pleasant month in Riley, Oregon, with an average temperature fluctuating between 51.1°F (10.6°C) and 72.3°F (22.4°C).Temperature
Riley, Oregon, in September demonstrates a small temperature transition, adjusting from an average high of a moderately hot 81.9°F (27.7°C) in August to an agreeable 72.3°F (22.4°C). Riley's nighttime temperature in September falls to an average of 51.1°F (10.6°C).Humidity
In Riley, the average relative humidity in September is 40%.Rainfall
In Riley, in September, during 5.2 rainfall days, 0.47" (12mm) of precipitation is typically accumulated. Throughout the year, there are 125.1 rainfall days, and 11.26" (286mm) of precipitation is accumulated.Snowfall
April through October are months without snowfall.Daylight
In September, the average length of the day is 12h and 29min.On the first day of the month, sunrise is at 6:22 am and sunset at 7:32 pm. On the last day of September, sunrise is at 6:55 am and sunset at 6:40 pm PDT.
Sunshine
In Riley, the average sunshine in September is 10.9h.UV index
In September, the average daily maximum UV index is 4. A UV Index reading of 3 to 5 represents a moderate health risk from unprotected exposure to Sun's UV rays for ordinary individuals.Note: In September, the maximum UV index of 4 suggests these recommendations:
Exercise caution. The susceptibility of light skin individuals to burns is less than 30 minutes. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Sun-related eye harm can be minimized with proper sunglasses offering UVA and UVB coverage.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Riley, OR
- Average high temperature in September: 72.3°F
The warmest month (with the highest average high temperature) is July (82.9°F).
The month with the lowest average high temperature is December (33.1°F).
- Average low temperature in September: 51.1°F
The month with the highest average low temperature is August (58.1°F).
The coldest month (with the lowest average low temperature) is December (21.2°F).
Average pressure in September
Riley, OR
- Average pressure in September: 29.98"Hg
The month with the highest atmospheric pressure is January (30.22"Hg).
The month with the lowest atmospheric pressure is August (29.94"Hg).
Average wind speed in September
Riley, OR
- Average wind speed in September: 7.6mph
The windiest month (with the highest average wind speed) is April (9.9mph).
The calmest month (with the lowest average wind speed) is August (7.5mph).
Average humidity in September
Riley, OR
- Average humidity in September: 40%
The month with the highest relative humidity is December (83%).
The months with the lowest relative humidity are July and August (33%).
Average rainfall in September
Riley, OR
- Average rainfall in September: 0.47"
The wettest month (with the highest rainfall) is December (1.54").
The driest month (with the least rainfall) is July (0.16").
Average rainfall days in September
Riley, OR
- Average rainfall days in September: 5.2 days
The month with the highest number of rainy days is March (17.7 days).
The month with the least rainy days is August (3.3 days).
Average snowfall in September
Riley, OR
- Average snowfall in September: 0"
The month with the highest snowfall is December (0.87").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Riley, OR
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is December (3.1 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
Riley, OR
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).
- Average sunshine in September: 10h and 54min
The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 5h and 12min).
Average sunshine days in September
Riley, OR
- Average sunshine days in September: 22.9 days
The months with the most sunshine days are July and August (25.3 days).
The month with the least sunshine days is March (11.5 days).
Average UV index in September
Riley, OR
- Average UV index in September: 4
The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in September
Riley, OR
- Average cloud cover in September: 14
The month with the most cloud cover is December (Cloud cover 47).
The months with the least cloud cover are July and August (Cloud cover 9).
Average visibility in September
Riley, OR
- 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).
