September weather forecast and climate
Modesto, CA

Weather in September

September, the first month of the autumn, in Modesto, is still a hot month, with average temperature ranging between max 90.9°F (32.7°C) and min 59.9°F (15.5°C).

Temperature

In Modesto, the average high-temperature slightly decreases, from a torrid 96.4°F (35.8°C) in August, to a hot 90.9°F (32.7°C). In September, in Modesto, the average low-temperature is 59.9°F (15.5°C).

Heat index

The average heat index in September is estimated at a hot 92.3°F (33.5°C). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
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', 'real feel', 'felt air temperature', or 'apparent temperature', is an index that combines air temperature and relative humidity to determine the human-perceived temperature equivalent. This effect is individual, with diverse people perceiving weather differently for numerous reasons (wind, pregnancy, differences in body mass, height, and shape), and activity. Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index 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

In Modesto, the average relative humidity is 41%.

Rainfall

In September, the rain falls for 1.6 days. Throughout September, 0.08" (2mm) of precipitation is accumulated. In Modesto, California, during the entire year, the rain falls for 54.3 days and collects up to 6.54" (166mm) of precipitation.

Daylight

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

Sunshine

In Modesto, the average sunshine is 11.5h.

UV index

The average daily maximum UV index in September is 6. A UV Index estimate of 6 to 7 represents a high threat to health from unsafe exposure to the UV radiation for the average person.
Note: The daily maximum UV index of 6 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. 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 Modesto?

In September, the average high-temperature is 90.9°F (32.7°C), and the average low-temperature is 59.9°F (15.5°C). In September, the average heat index (a.k.a. 'real feel', 'apparent temperature'), that combines both air temperature and relative humidity, is estimated at 92.3°F (33.5°C).

What is the average humidity in September in Modesto?

In September, the average relative humidity is 41%.

How much does it rain in Modesto in September?

In September, in Modesto, California, the rain falls for 1.6 days. Throughout September, 0.08" (2mm) of precipitation is accumulated.

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

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

How long on average sun shines in September in Modesto?

In September, the average sunshine is 11.5h.

How high is the UV index in September in Modesto?

In Modesto, California, the average daily maximum UV index in September is 6. A UV Index reading of 6 to 7 represents a high health vulnerability from the exposure to the Sun's UV rays.

Average temperature in September
Modesto, CA

Average temperature in September - Modesto, CA
  • Average high temperature in September: 90.9°F

The warmest month (with the highest average high temperature) is July (97.7°F).
The month with the lowest average high temperature is December (55.6°F).

  • Average low temperature in September: 59.9°F

The month with the highest average low temperature is July (62.1°F).
The coldest months (with the lowest average low temperature) are January and December (41.9°F).

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Average pressure in September
Modesto, CA

Average pressure in September - Modesto, CA
  • Average pressure in September: 29.93"

The month with the highest atmospheric pressure is January (30.15").
The month with the lowest atmospheric pressure is June (29.91").

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Average wind speed in September
Modesto, CA

Average wind speed in September - Modesto, CA
  • Average wind speed in September: 5.8mph

The windiest month (with the highest average wind speed) is June (7.3mph).
The calmest month (with the lowest average wind speed) is November (5.2mph).

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Average humidity in September
Modesto, CA

Average humidity in September - Modesto, CA
  • Average humidity in September: 41%

The month with the highest relative humidity is January (72%).
The month with the lowest relative humidity is July (37%).

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Average rainfall in September
Modesto, CA

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

The wettest month (with the highest rainfall) is March (1.3").
The driest months (with the least rainfall) are July and August (0.04").

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Average rainfall days in September
Modesto, CA

Average rainfall days in September - Modesto, CA
  • Average rainfall days in September: 1.6 days

The month with the highest number of rainy days is March (10.3 days).
The month with the least rainy days is August (0.9 days).

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

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

The month with the longest days is June (Average daylight: 14.7h).
The month with the shortest days is December (Average daylight: 9.6h).

  • Average sunshine in September: 11.5h

The month with the most sunshine is July (Average sunshine: 12.1h).
The month with the least sunshine is December (Average sunshine: 6h).

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Average sunshine days in September
Modesto, CA

Average sunshine days in September - Modesto, CA
  • Average sunshine days in September: 27.1 days

The month with the most sunshine days is August (29.2 days).
The month with the least sunshine days is March (19.6 days).

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Average UV index in September
Modesto, CA

Average UV index in September - Modesto, 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, February, November and December (UV index 3).

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Average cloud cover in September
Modesto, CA

Average cloud cover in September - Modesto, CA
  • Average cloud cover in September: 6

The month with the most cloud cover is March (Cloud cover 33).
The month with the least cloud cover is July (Cloud cover 4).

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Average visibility in September
Modesto, CA

Average visibility in September - Modesto, 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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