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 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
The onset of September results in a small decrease in the average high-temperature, moderately receding from a very hot 100.9°F (38.3°C) in August to a hot 94.1°F (34.5°C). Riverdale registers a significant drop in temperature in September, with average nighttime lows of 63.1°F (17.3°C).Humidity
In September, the average relative humidity is 33%.Rainfall
In Riverdale, California, in September, during 1.9 rainfall days, 0.12" (3mm) of precipitation is typically accumulated. Throughout the year, there are 58.2 rainfall days, and 9.29" (236mm) of precipitation is accumulated.Daylight
In Riverdale, the average length of the day in September is 12h and 24min.On the first day of the month, sunrise is at 6:31 am and sunset at 7:26 pm. On the last day of September, sunrise is at 6:54 am and sunset at 6:43 pm PDT.
Sunshine
In September, the average sunshine is 11.3h.UV index
In Riverdale, the average daily maximum UV index in September is 6. A UV Index value of 6 to 7 symbolizes a high health vulnerability from exposure to the Sun's UV rays for average individuals.Note: In September, the UV index of 6 transforms into the following advice:
Incorporate safeguards and honour sun safety principles. Protection from skin and eye damage is obligatory. Between 10 a.m. and 4 p.m., UV radiation is strongest. Make an effort to avoid direct sunlight during this time, remembering that shade structures may not provide full sun protection. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How hot is it in September?
What is the average humidity in September?
How much does it rain in September?
How many hours of daylight does Riverdale have in September?
What time are sunrise and sunset in September?
How many hours of sunshine does Riverdale have in September?
What is the UV index reading in September?
Average temperature in September
Riverdale, CA
- Average high temperature in September: 94.1°F
The warmest month (with the highest average high temperature) is July (102.2°F).
The month with the lowest average high temperature is December (57.2°F).
- Average low temperature in September: 63.1°F
The month with the highest average low temperature is July (66.9°F).
The coldest month (with the lowest average low temperature) is December (43°F).
Average pressure in September
Riverdale, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
Riverdale, CA
- Average wind speed in September: 5.7mph
The windiest month (with the highest average wind speed) is June (7.1mph).
The calmest months (with the lowest average wind speed) are January and November (4.8mph).
Average humidity in September
Riverdale, CA
- Average humidity in September: 33%
The months with the highest relative humidity are January and December (66%).
The month with the lowest relative humidity is July (30%).
Average rainfall in September
Riverdale, CA
- Average rainfall in September: 0.12"
The wettest months (with the highest rainfall) are January, February and March (1.54").
The driest month (with the least rainfall) is August (0.08").
Average rainfall days in September
Riverdale, CA
- Average rainfall days in September: 1.9 days
The month with the highest number of rainy days is March (9.6 days).
The month with the least rainy days is August (0.8 days).
Average daylight in September /
Average sunshine in September
Riverdale, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 36min).
The month with the shortest days is December (Average daylight: 9h and 42min).
- Average sunshine in September: 11h and 2min
The months with the most sunshine are June and July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 6h and 24min).
Average sunshine days in September
Riverdale, CA
- Average sunshine days in September: 27.4 days
The month with the most sunshine days is August (29.3 days).
The month with the least sunshine days is February (19.4 days).
Average UV index in September
Riverdale, CA
- Average UV index in September: 6
The months with the highest UV index are June, July and August (UV index 7).
The months with the lowest UV index are January, November and December (UV index 3).
Average cloud cover in September
Riverdale, CA
- Average cloud cover in September: 5
The months with the most cloud cover are March and December (Cloud cover 28).
The month with the least cloud cover is August (Cloud cover 4).
Average visibility in September
Riverdale, CA
- 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).
Riverdale, California, USA
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