Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
With the beginning of September, the average high-temperature shows a decrease, transitioning from a warm 82.4°F (28°C) in August to an agreeable 70.9°F (21.6°C). Despite the high peak temperatures, Riverside witnesses an average nighttime cooling to a frosty 47.3°F (8.5°C) in September.Humidity
In September, the average relative humidity in Riverside is 52%.Rainfall
In Riverside, in September, it is raining for 5.3 days, with typically 0.51" (13mm) of accumulated precipitation. Throughout the year, there are 90.2 rainfall days, and 7.56" (192mm) of precipitation is accumulated.Snowfall
May through October are months without snowfall.Daylight
The average length of the day in September in Riverside is 12h and 34min.On the first day of the month, sunrise is at 6:16 am and sunset at 7:38 pm. On the last day of September, sunrise is at 6:57 am and sunset at 6:38 pm PDT.
Sunshine
In Riverside, the average sunshine in September is 10.8h.UV index
In September, the average daily maximum UV index in Riverside is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV rays for ordinary individuals.Note: The UV index of 4 during September translates into the following guidance:
Guard yourself - Avoiding sunburn is suggested. Midday is the peak time for the Sun's radiation; stay in the shade and protect yourself. Experience reduced UV exposure by about half when donning a wide-brim hat.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures in Riverside?
What is the average humidity in September in Riverside?
How many days does it rain in September in Riverside?
When it does not snow in Riverside?
What is the average length of the day in September in Riverside?
When is the sunrise / sunset in September in Riverside?
How long on average sun shines in September in Riverside?
How high is the UV index in September in Riverside?
Average temperature in September
Riverside, WA
- Average high temperature in September: 70.9°F
The warmest month (with the highest average high temperature) is July (82.6°F).
The month with the lowest average high temperature is December (30.4°F).
- Average low temperature in September: 47.3°F
The month with the highest average low temperature is August (55°F).
The coldest month (with the lowest average low temperature) is December (18.1°F).
Average pressure in September
Riverside, WA
- Average pressure in September: 29.97"Hg
The month with the highest atmospheric pressure is January (30.17"Hg).
The months with the lowest atmospheric pressure are June and August (29.93"Hg).
Average wind speed in September
Riverside, WA
- Average wind speed in September: 4.7mph
The windiest month (with the highest average wind speed) is April (5.1mph).
The calmest month (with the lowest average wind speed) is January (4mph).
Average humidity in September
Riverside, WA
- Average humidity in September: 52%
The month with the highest relative humidity is January (91%).
The months with the lowest relative humidity are July and August (42%).
Average rainfall in September
Riverside, WA
- Average rainfall in September: 0.51"
The wettest month (with the highest rainfall) is December (0.94").
The driest months (with the least rainfall) are July and August (0.2").
Average rainfall days in September
Riverside, WA
- Average rainfall days in September: 5.3 days
The month with the highest number of rainy days is March (11.5 days).
The month with the least rainy days is August (2.8 days).
Average snowfall in September
Riverside, WA
- Average snowfall in September: 0"
The month with the highest snowfall is January (3.39").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Riverside, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is December (8.4 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Riverside, WA
- Average daylight in September: 12h and 4min
The month with the longest days is June (Average daylight: 16h and 6min).
The month with the shortest days is December (Average daylight: 8h and 24min).
- Average sunshine in September: 10h and 5min
The months with the most sunshine are July and August (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 4h and 30min).
Average sunshine days in September
Riverside, WA
- Average sunshine days in September: 23.4 days
The month with the most sunshine days is August (26.3 days).
The month with the least sunshine days is November (15.4 days).
Average UV index in September
Riverside, WA
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The month with the lowest UV index is November (UV index 1).
Average cloud cover in September
Riverside, WA
- Average cloud cover in September: 18
The month with the most cloud cover is January (Cloud cover 49).
The months with the least cloud cover are July and August (Cloud cover 12).
Average visibility in September
Riverside, WA
- Average visibility in September: 6mi
The months with the highest visibility are April, May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February and December (4mi).
Riverside, Washington, USA
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