September weather forecast and climate
Riverdale, CA

Weather in September

The first month of the autumn, September, is also a hot month in Riverdale, California, with temperature in the range of an average high of 94.1°F (34.5°C) and an average low of 63.1°F (17.3°C).

Temperature

In Riverdale, the average high-temperature slightly decreases, from a torrid 100.9°F (38.3°C) in August, to a hot 94.1°F (34.5°C). In September, the average low-temperature is 63.1°F (17.3°C).

Humidity

The average relative humidity in Riverdale is 33%.

Rainfall

In Riverdale, it is raining for 1.9 days, with typically 0.12" (3mm) of accumulated precipitation. In Riverdale, during the entire year, the rain falls for 58.2 days and collects up to 9.29" (236mm) of precipitation.

Daylight

The average length of the day in Riverdale is 12.4h.

Sunshine

In September, the average sunshine in Riverdale is 11.3h.

UV index

In September, the average daily maximum UV index is 6. A UV Index estimate of 6 to 7 represents a high health risk from unsafe exposure to the UV radiation for the average person.
Note: The daily maximum UV index of 6 in September interpret into the following advice:
Take precautions against overexposure. Fair-skinned people may get burned in less than 20 minutes. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.
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FAQ

What is the temperature in September in Riverdale?

In Riverdale, California, in September, the average high-temperature is 94.1°F (34.5°C), and the average low-temperature is 63.1°F (17.3°C).

What is the average humidity in September in Riverdale?

In Riverdale, California, the average relative humidity in September is 33%.

How much does it rain in Riverdale in September?

In September, in Riverdale, California, the rain falls for 1.9 days. Throughout September, 0.12" (3mm) of precipitation is accumulated.

What is the average length of the day in September in Riverdale?

In Riverdale, California, the average length of the day in September is 12.4h.

How long on average sun shines in September in Riverdale?

The average sunshine in September in Riverdale, California, is 11.3h.

What is the UV index reading in September in Riverdale?

In September, the average daily maximum UV index in Riverdale, California, is 6. A UV Index of 6 to 7 symbolizes a high hazard to health from the exposure to the Sun's UV radiation.

Average temperature in September
Riverdale, CA

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).

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Average pressure in September
Riverdale, CA

Average pressure in September - Riverdale, CA
  • Average pressure in September: 29.92"

The month with the highest atmospheric pressure is January (30.14").
The month with the lowest atmospheric pressure is June (29.89").

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Average wind speed in September
Riverdale, CA

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).

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Average humidity in September
Riverdale, CA

Average humidity in September - Riverdale, CA
  • Average humidity in September: 33%

Months with the highest relative humidity are January and December (66%).
The month with the lowest relative humidity is July (30%).

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Average rainfall in September
Riverdale, CA

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").

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Average rainfall days in September
Riverdale, CA

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).

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Average daylight in September /
Average sunshine in September
Riverdale, CA

Average daylight in September / Average sunshine in September - Riverdale, CA
  • Average daylight in September: 12.4h

The month with the longest days is June (Average daylight: 14.6h).
The month with the shortest days is December (Average daylight: 9.7h).

  • Average sunshine in September: 11.3h

Months with the most sunshine are June and July (Average sunshine: 12.1h).
The month with the least sunshine is December (Average sunshine: 6.4h).

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Average sunshine days in September
Riverdale, CA

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).

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Average UV index in September
Riverdale, CA

Average UV index in September - Riverdale, CA
  • Average UV index in September: 6

Months with the highest UV index are June, July and August (UV index 7).
Months with the lowest UV index are January, November and December (UV index 3).

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Average cloud cover in September
Riverdale, CA

Average cloud cover in September - Riverdale, CA
  • Average cloud cover in September: 5

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).

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Average visibility in September
Riverdale, CA

Average visibility in September - Riverdale, CA
  • Average visibility in September: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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