September weather forecastTri-City, OR
September
Weather in September
September, the first month of the autumn in Tri-City, is also a moderately hot month, with temperature in the range of an average high of 74.5°F (23.6°C) and an average low of 44.8°F (7.1°C).Temperature
Transition into September subtly marks a drop in the average high-temperature, moderately moving from 81.1°F (27.3°C) in August to a still warm 74.5°F (23.6°C). Throughout September nights, Tri-City reports a steady thermal contrast from the day, with an average low-temperature of 44.8°F (7.1°C).Humidity
The average relative humidity in September is 72%.Rainfall
In Tri-City, in September, during 3.6 rainfall days, 0.31" (8mm) of precipitation is typically accumulated. In Tri-City, during the entire year, the rain falls for 93.9 days and collects up to 7.64" (194mm) of precipitation.Snowfall
In Tri-City, snow does not fall in April through October.Daylight
The average length of the day in September is 12h and 29min.On the first day of the month, sunrise is at 6:38 am and sunset at 7:47 pm. On the last day of September, sunrise is at 7:10 am and sunset at 6:55 pm PDT.
Sunshine
In September, the average sunshine is 9.7h.UV index
In Tri-City, the average daily maximum UV index in September is 3. A UV Index reading of 3 to 5 represents a moderate health risk from exposure to the Sun's UV radiation for average individuals.Note: The daily high UV index of 3 in September translates into this advice:
Exercise prevention - Precautions against solar damage are endorsed. During midday, the Sun's radiation is strongest, and it's advisable to reduce direct exposure. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Tri-City, OR
- Average high temperature in September: 74.5°F
The warmest month (with the highest average high temperature) is August (81.1°F).
The month with the lowest average high temperature is December (45.7°F).
- Average low temperature in September: 44.8°F
The month with the highest average low temperature is August (47.7°F).
The coldest month (with the lowest average low temperature) is December (32.2°F).
Average pressure in September
Tri-City, 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
Tri-City, OR
- Average wind speed in September: 3.2mph
The windiest month (with the highest average wind speed) is January (4.1mph).
The calmest month (with the lowest average wind speed) is September (3.2mph).
Average humidity in September
Tri-City, OR
- Average humidity in September: 72%
The months with the highest relative humidity are January, February and December (86%).
The month with the lowest relative humidity is August (69%).
Average rainfall in September
Tri-City, OR
- Average rainfall in September: 0.31"
The wettest months (with the highest rainfall) are January, February and December (1.1").
The driest months (with the least rainfall) are July and August (0.16").
Average rainfall days in September
Tri-City, OR
- Average rainfall days in September: 3.6 days
The month with the highest number of rainy days is March (12.6 days).
The month with the least rainy days is August (2.4 days).
Average snowfall in September
Tri-City, OR
- Average snowfall in September: 0"
The month with the highest snowfall is February (0.87").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Tri-City, OR
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (1.5 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
Tri-City, OR
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 18min).
The month with the shortest days is December (Average daylight: 9h and 6min).
- Average sunshine in September: 9h and 42min
The month with the most sunshine is August (Average sunshine: 11h and 18min).
The month with the least sunshine is December (Average sunshine: 4h and 18min).
Average sunshine days in September
Tri-City, OR
- Average sunshine days in September: 25.9 days
The month with the most sunshine days is August (26.5 days).
The month with the least sunshine days is March (16.1 days).
Average UV index in September
Tri-City, OR
- Average UV index in September: 3
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
Tri-City, OR
- Average cloud cover in September: 31
The month with the most cloud cover is March (Cloud cover 60).
The month with the least cloud cover is August (Cloud cover 25).
Average visibility in September
Tri-City, OR
- Average visibility in September: 5mi
The months with the highest visibility are July, August and September (5mi).
The months with the lowest visibility are January, February, March, April, May, June, October, November and December (4mi).
