Brentwood
California, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Brentwood, CA

An aerial shot of scenic and organized home community in Brentwood City, California
An aerial shot of scenic and organized home community in Brentwood City, California
The first month of the autumn, September, is also a moderately hot month in Brentwood, California, with temperature in the range of an average low of 57.7°F (14.3°C) and an average high of 85.3°F (29.6°C).

Temperature

In September, the average high-temperature is relatively the same as in August - a warm 85.3°F (29.6°C). In September, in Brentwood, the average low-temperature is 57.7°F (14.3°C).

Heat index

The average heat index is calculated to a hot 87.4°F (30.8°C). Constant exposure and activity lead to possible fatigue. Prolonged exercise may result in heat cramps.
Take into consideration that the heat index values are calculated for shade and light wind conditions. 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', 'felt air temperature', or 'real feel', is a measure of how hot it feels when the actual air humidity is factored in. This effect is individual, with diverse people perceiving weather differently for numerous reasons (differences in body mass, height, and shape, pregnancy, metabolic differences), and activity. 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 least humid month is September, with an average relative humidity of 52%.

Rainfall

In Brentwood, California, during 1.3 rainfall days, 0.08" (2mm) of precipitation is typically accumulated. Throughout the year, there are 62 rainfall days, and 10.16" (258mm) of precipitation is accumulated.

Snowfall

In Brentwood snow does not fall in January through November.

Daylight

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

Sunshine

In September, the average sunshine in Brentwood is 11.2h.

UV index

In Brentwood, the average daily maximum UV index is 5. A UV Index estimate of 3 to 5 represents a moderate threat to health from the exposure to the Sun's UV rays for average individuals.
Note: The average daily UV index of 5 in September transform into the following instructions:
Take precautions - Protection against the skin and eye damage is obliged. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. 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.

What is the temperature in September in Brentwood?

In Brentwood, California, in September, the average high-temperature is 85.3°F (29.6°C), and the average low-temperature is 57.7°F (14.3°C). In September, the average heat index (a.k.a. 'feels like', 'felt air temperature'), that calculates temperature value influenced by the moisture in the air, is estimated at 87.4°F (30.8°C).

What is the least humid month in Brentwood?

The least humid month in Brentwood, California, is September, with an average relative humidity of 52%.

What is the average humidity in September in Brentwood?

In Brentwood, the average relative humidity in September is 52%.

How many days does it rain in September in Brentwood?

In Brentwood, during September, the rain falls for 1.3 days and regularly aggregates up to 0.08" (2mm) of precipitation.

When it does not snow in Brentwood?

January through November are months without snowfall in Brentwood.

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

The average length of the day in September in Brentwood, California, is 12.4h.

How long on average sun shines in September in Brentwood?

The average sunshine in September is 11.2h.

What is the UV index reading in September in Brentwood?

The average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a medium hazard to health from the exposure to the Sun's UV rays.
Average temperature in September - Brentwood, CA
  • Average high temperature in September: 85.3°F

The warmest month (with the highest average high temperature) is July (88.5°F).
The month with the lowest average high temperature is December (55°F).

  • Average low temperature in September: 57.7°F

The month with the highest average low temperature is September (57.7°F).
The coldest month (with the lowest average low temperature) is January (41.5°F).

Average humidity in September - Brentwood, CA
  • Average humidity in September: 52%

The month with the highest relative humidity is January (74%).
The month with the lowest relative humidity is September (52%).

Average rainfall in September - Brentwood, CA
  • Average rainfall in September: 0.08"

The wettest month (with the highest rainfall) is February (2.09").
Driest months (with the lowest rainfall) are July and August (0.04").

Average rainfall days in September - Brentwood, CA
  • Average rainfall days in September: 1.3 days

The month with the highest number of rainy days is March (12.3 days).
The month with the lowest number of rainy days is August (0.8 days).

Average snowfall days in September - Brentwood, CA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is December (0.1 days).
Months with the lowest number of snowfall days are January, February, March, April, May, June, July, August, September, October and November (0 days).

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

The month with the longest days is June (Average daylight: 14.8h).
The month with shortest days is December (Average daylight: 9.6h).

  • Average sunshine in September: 11.2h

The month with most sunshine is July (Average sunshine: 12.1h).
The month with least sunshine is December (Average sunshine: 5.8h).

Average UV index in September - Brentwood, CA
  • Average UV index in September: 5

Months with the highest UV index are June, July and August (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 3).