September weather forecast and climate
Sun Valley, CA

Weather in September

September, the first month of the autumn, in Sun Valley, is still a warm month, with average temperature varying between 63.1°F (17.3°C) and 83.3°F (28.5°C).

Temperature

In September, the average high-temperature is almost the same as in August - a warm 83.3°F (28.5°C). The average low-temperature, in Sun Valley, is 63.1°F (17.3°C).

Heat index

The average heat index in September is estimated at 84.4°F (29.1°C). Constant exposure and activity lead to possible fatigue. Prolonged exercise may result in heat cramps.
Note that heat index values are valued for light wind and location in the shade. With the exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like', 'apparent temperature', 'real feel', or 'felt air temperature', is a measure that combines both air temperature and relative humidity into a single value that indicates how hot the weather feels. Additional factors like activity, metabolic differences, wind, and pregnancy affect individual temperature impact. Be aware that direct exposure to sunlight increases heat impact, and may raise the heat index additionally, by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.

Humidity

The average relative humidity in September is 51%.

Rainfall

In September, in Sun Valley, the rain falls for 2.7 days. Throughout September, 0.16" (4mm) of precipitation is accumulated. Throughout the year, in Sun Valley, California, there are 40.1 rainfall days, and 5.87" (149mm) of precipitation is accumulated.

Daylight

The average length of the day in Sun Valley is 12.4h.

Sunshine

In September, the average sunshine in Sun Valley is 10.8h.

UV index

Months with the highest UV index are June through September, with an average maximum UV index of 6. A UV Index value of 6 to 7 symbolizes a high health risk from unprotected exposure to the Sun's UV rays for the ordinary person.
Note: In September, the average maximum UV index of 6 translate into the following recommendations:
Take precautions and utilize sun safety practices. Protection against the skin and eye damage is required. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.
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FAQ

What is the temperature in September in Sun Valley?

In Sun Valley, California, in September, the average high-temperature is 83.3°F (28.5°C), and the average low-temperature is 63.1°F (17.3°C). The average heat index (a.k.a. 'apparent temperature', 'feels like'), that combines both air temperature and relative humidity, in September is appraised at 84.4°F (29.1°C).

What is the average humidity in September in Sun Valley?

The average relative humidity in September in Sun Valley is 51%.

How many days does it rain in September in Sun Valley?

In September, in Sun Valley, the rain falls for 2.7 days. Throughout September, 0.16" (4mm) of precipitation is accumulated.

How many hours of daylight does Sun Valley have in September?

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

How long on average sun shines in September in Sun Valley?

The average sunshine in September in Sun Valley is 10.8h.

What is the month with the highest UV index in Sun Valley?

June through September, with an average maximum UV index of 6, are months with the highest UV index.

What is the UV index intensity in September in Sun Valley?

In Sun Valley, the average daily maximum UV index in September is 6. A UV Index value of 6 to 7 symbolizes a high health vulnerability from unsafe exposure to the Sun's UV rays.

Average temperature in September
Sun Valley, CA

Average temperature in September - Sun Valley, CA
  • Average high temperature in September: 83.3°F

The warmest month (with the highest average high temperature) is August (86.5°F).
The month with the lowest average high temperature is December (61.7°F).

  • Average low temperature in September: 63.1°F

The month with the highest average low temperature is August (64.8°F).
The coldest month (with the lowest average low temperature) is December (46.2°F).

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Average pressure in September
Sun Valley, CA

Average pressure in September - Sun Valley, CA
  • Average pressure in September: 29.89"

The month with the highest atmospheric pressure is January (30.11").
The month with the lowest atmospheric pressure is June (29.88").

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Average wind speed in September
Sun Valley, CA

Average wind speed in September - Sun Valley, CA
  • Average wind speed in September: 4.4mph

The windiest month (with the highest average wind speed) is April (5.9mph).
The calmest month (with the lowest average wind speed) is September (4.4mph).

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Average humidity in September
Sun Valley, CA

Average humidity in September - Sun Valley, CA
  • Average humidity in September: 51%

The month with the highest relative humidity is June (59%).
The month with the lowest relative humidity is November (48%).

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Average rainfall in September
Sun Valley, CA

Average rainfall in September - Sun Valley, CA
  • Average rainfall in September: 0.16"

The wettest month (with the highest rainfall) is December (1.18").
The driest month (with the least rainfall) is June (0.04").

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Average rainfall days in September
Sun Valley, CA

Average rainfall days in September - Sun Valley, CA
  • Average rainfall days in September: 2.7 days

The month with the highest number of rainy days is March (5.2 days).
The month with the least rainy days is June (1 days).

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Average daylight in September /
Average sunshine in September
Sun Valley, CA

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

The month with the longest days is June (Average daylight: 14.4h).
The month with the shortest days is December (Average daylight: 9.9h).

  • Average sunshine in September: 10.8h

Months with the most sunshine are June, July and August (Average sunshine: 12.1h).
Months with the least sunshine are January, February and December (Average sunshine: 6.9).

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Average sunshine days in September
Sun Valley, CA

Average sunshine days in September - Sun Valley, CA
  • Average sunshine days in September: 25 days

The month with the most sunshine days is October (27.1 days).
The month with the least sunshine days is February (22.9 days).

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Average UV index in September
Sun Valley, CA

Average UV index in September - Sun Valley, CA
  • Average UV index in September: 6

Months with the highest UV index are June, July, August and September (UV index 6).
The month with the lowest UV index is December (UV index 3).

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Average cloud cover in September
Sun Valley, CA

Average cloud cover in September - Sun Valley, CA
  • Average cloud cover in September: 6

Months with the most cloud cover are March and December (Cloud cover 21).
The month with the least cloud cover is August (Cloud cover 4).

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Average visibility in September
Sun Valley, CA

Average visibility in September - Sun Valley, 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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