September weather forecastRichland, WA
September
Weather in September
September brings a significant change in the climate of Richland as the autumn season kicks in. The temperatures begin to drop noticeably and the greenery starts turning rustic, indicating summer's end. The typically clear September skies are now interspersed with clouds. Though the city experiences a nominal amount of rainfall, around 0.2" (5mm). Sunny days followed by cool evenings are a common sight in September, signaling a transition toward the cooler months.Temperature
The arrival of September corresponds with a shift in temperature, down from a hot 89.4°F (31.9°C) in August to a warm 78.6°F (25.9°C). Richland in September experiences a low-temperature average of 57°F (13.9°C).Humidity
In September, the average relative humidity is 43%.Rainfall
The months with the least rainfall are July and September Rain falls for 4 days and accumulates 0.2" (5mm) of rain.Snowfall
April through October are months without snowfall.Daylight
The average length of the day in September is 12h and 32min.On the first day of the month, sunrise is at 6:18 am and sunset at 7:35 pm. On the last day of September, sunrise is at 6:55 am and sunset at 6:38 pm PDT.
Sunshine
In September, the average sunshine is 10.9h.UV index
In Richland, the average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for the average person.Note: The maximum UV index of 5 during September translates into these guidelines:
Ensure safety - Imperative it is to shield skin and eyes from damage. Stay safe from the Sun's strongest UV rays by limiting exposure during midday. Sunglasses that ward off UVA and UVB rays play a pivotal role in reducing solar eye damage.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Richland, WA
- Average high temperature in September: 78.6°F
The warmest month (with the highest average high temperature) is July (90.1°F).
The month with the lowest average high temperature is December (38.1°F).
- Average low temperature in September: 57°F
The month with the highest average low temperature is August (64.2°F).
The coldest month (with the lowest average low temperature) is December (27.5°F).
Average pressure in September
Richland, WA
- Average pressure in September: 29.95"Hg
The month with the highest atmospheric pressure is January (30.18"Hg).
The month with the lowest atmospheric pressure is August (29.91"Hg).
Average wind speed in September
Richland, WA
- Average wind speed in September: 6.6mph
The windiest month (with the highest average wind speed) is April (8.3mph).
The calmest month (with the lowest average wind speed) is December (5.6mph).
Average humidity in September
Richland, WA
- Average humidity in September: 43%
The month with the highest relative humidity is January (81%).
The month with the lowest relative humidity is July (35%).
Average rainfall in September
Richland, WA
- Average rainfall in September: 0.2"
The wettest month (with the highest rainfall) is December (0.94").
The driest months (with the least rainfall) are July and September (0.2").
Average rainfall days in September
Richland, WA
- Average rainfall days in September: 4 days
The month with the highest number of rainy days is March (12.3 days).
The month with the least rainy days is July (3.5 days).
Average snowfall in September
Richland, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (2.2").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
Richland, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is December (3.3 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
Richland, WA
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 42min).
The month with the shortest days is December (Average daylight: 8h and 42min).
- 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 January (Average sunshine: 5h and 24min).
Average sunshine days in September
Richland, WA
- Average sunshine days in September: 24.2 days
The month with the most sunshine days is July (25.7 days).
The months with the least sunshine days are February and March (15.3 days).
Average UV index in September
Richland, WA
- Average UV index in September: 5
The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Richland, WA
- Average cloud cover in September: 16
The month with the most cloud cover is January (Cloud cover 44).
The month with the least cloud cover is July (Cloud cover 9).
Average visibility in September
Richland, WA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
