September weather forecast and climate
Gilroy, CA

A colorful sunset sky over the hilly region of Gilroy in California
A colorful sunset sky over the hilly region of Gilroy in California

Weather in September

September, the first month of the autumn, in Gilroy, is also a moderately hot month, with average temperature varying between 83.3°F (28.5°C) and 54.1°F (12.3°C).

Temperature

In Gilroy, California, the average high-temperature is relatively the same as in August - a still warm 83.3°F (28.5°C). The average low-temperature, in Gilroy, California, is 54.1°F (12.3°C).

Heat index

In September, the average heat index is estimated at 85.6°F (29.8°C). Exhaustion is likely with prolonged exposure and activity. Sustaining activity 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 'apparent temperature', 'real feel', 'felt air temperature', or 'feels like', is calculated by taking the relative humidity value for a specific location and factoring it into the air temperature reading. Additional factors like activity, clothing, wind, and pregnancy affect individual temperature impact. 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

September is the least humid month in Gilroy, with an average relative humidity of 57%.

Rainfall

January through May, September through December are months with rainfall. September is the first month it rains. Throughout September, in the average 1.7 rainfall days, it receives 0.04" (1mm) of precipitation. In Gilroy, during the entire year, the rain falls for 43.4 days and collects up to 3.66" (93mm) of precipitation.

Daylight

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

Sunshine

The average sunshine in September is 11.3h.

UV index

In September, the average daily maximum UV index in Gilroy is 5. A UV Index estimate of 3 to 5 represents a moderate health risk from unprotected exposure to the Sun's UV rays for the ordinary person.
Note: The daily maximum UV index of 5 interpret into the following advice:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. 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 Gilroy?

The average high-temperature, in September, in Gilroy, is 83.3°F (28.5°C), while the average low-temperature is 54.1°F (12.3°C). In September, the average heat index (a.k.a. 'apparent temperature', 'real feel'), that represents influence of the relative humidity to air temperaure, is calculated to 85.6°F (29.8°C).

What is the least humid month in Gilroy?

With an average relative humidity of 57%, September is the least humid month.

What is the average humidity in September in Gilroy?

The average relative humidity in September is 57%.

When does it start to rain in Gilroy?

September is the first month it rains in Gilroy, California. Throughout September, in the average 1.7 rainfall days, it receives 0.04" (1mm) of precipitation.

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

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

How long on average sun shines in September in Gilroy?

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

What is the UV index reading in September in Gilroy?

In September, the average daily maximum UV index in Gilroy is 5. A UV Index value of 3 to 5 symbolizes a moderate vulnerability from the exposure to the Sun's UV rays.

Average temperature in September
Gilroy, CA

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

The warmest month (with the highest average high temperature) is August (85.1°F).
The month with the lowest average high temperature is December (57.6°F).

  • Average low temperature in September: 54.1°F

Months with the highest average low temperature are August and September (54.1°F).
The coldest months (with the lowest average low temperature) are February and March (40.6°F).

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Average pressure in September
Gilroy, CA

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

The month with the highest atmospheric pressure is January (30.14").
Months with the lowest atmospheric pressure are June, August and September (29.92").

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Average wind speed in September
Gilroy, CA

Average wind speed in September - Gilroy, CA
  • Average wind speed in September: 4.2mph

The windiest month (with the highest average wind speed) is May (5.3mph).
The calmest month (with the lowest average wind speed) is November (3.9mph).

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Average humidity in September
Gilroy, CA

Average humidity in September - Gilroy, CA
  • Average humidity in September: 57%

The month with the highest relative humidity is March (74%).
The month with the lowest relative humidity is September (57%).

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Average rainfall in September
Gilroy, CA

Average rainfall in September - Gilroy, CA
  • Average rainfall in September: 0.04"

The wettest month (with the highest rainfall) is December (0.83").
The driest months (with the least rainfall) are June, July and August (0").

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Average rainfall days in September
Gilroy, CA

Average rainfall days in September - Gilroy, CA
  • Average rainfall days in September: 1.7 days

The month with the highest number of rainy days is March (8.3 days).
The month with the least rainy days is August (0.6 days).

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

Average daylight in September / Average sunshine in September - Gilroy, 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: 9.7h).

  • Average sunshine in September: 11.3h

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
Gilroy, CA

Average sunshine days in September - Gilroy, CA
  • Average sunshine days in September: 27.7 days

The month with the most sunshine days is July (29.9 days).
The month with the least sunshine days is March (21.4 days).

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Average UV index in September
Gilroy, CA

Average UV index in September - Gilroy, 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).

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Average cloud cover in September
Gilroy, CA

Average cloud cover in September - Gilroy, CA
  • Average cloud cover in September: 9

The month with the most cloud cover is March (Cloud cover 35).
The month with the least cloud cover is July (Cloud cover 7).

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Average visibility in September
Gilroy, CA

Average visibility in September - Gilroy, 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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