September weather forecast and climate
La Mesa, CA

Weather in September

September, the first month of the autumn, in La Mesa, is still a warm month, with temperature in the range of an average low of 64.4°F (18°C) and an average high of 81.5°F (27.5°C).

Temperature

In La Mesa, California, the average high-temperature is relatively the same as in August - a still moderately hot 81.5°F (27.5°C). In La Mesa, in September, the average low-temperature is 64.4°F (18°C).

Heat index

The average heat index in September is evaluated at 83.8°F (28.8°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 'real feel', 'feels like', 'felt air temperature', or 'apparent temperature', combines air temperature and relative humidity to represent a human perceived temperature equivalent. Additional factors like activity, wind, clothing, and differences in body mass, height, and shape 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 La Mesa is 61%.

Rainfall

In La Mesa, during 3.7 rainfall days, 0.28" (7mm) of precipitation is typically accumulated. In La Mesa, during the entire year, the rain falls for 54.5 days and collects up to 6.57" (167mm) of precipitation.

Daylight

In La Mesa, the average length of the day is 12.4h.

Sunshine

In La Mesa, the average sunshine in September is 10.3h.

UV index

Months with the highest UV index in La Mesa, California, are June through September, with an average maximum UV index of 6. A UV Index reading of 6 to 7 represents a high health risk from unprotected exposure to the Sun's UV rays for average individuals.
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 La Mesa?

The average high-temperature, in September, in La Mesa, is 81.5°F (27.5°C), while the average low-temperature is 64.4°F (18°C). In September, the average heat index (a.k.a. 'apparent temperature', 'feels like'), that factores the actual air temperature with the relative humidity, is calculated to 83.8°F (28.8°C).

What is the average humidity in September in La Mesa?

In September, the average relative humidity in La Mesa is 61%.

How many days does it rain in September in La Mesa?

In September, the rain falls for 3.7 days. Throughout September, 0.28" (7mm) of precipitation is accumulated.

What is the average length of the day in September in La Mesa?

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

How many hours of sunshine does La Mesa have in September?

In La Mesa, the average sunshine in September is 10.3h.

What is the month with the highest UV index in La Mesa?

Months with the highest UV index in La Mesa are June through September, with an average maximum UV index of 6.

What is the UV index reading in September in La Mesa?

The average daily maximum UV index in September is 6. A UV Index of 6 to 7 symbolizes a high health threat from the exposure to the Sun's UV rays.

Average temperature in September
La Mesa, CA

Average temperature in September - La Mesa, CA
  • Average high temperature in September: 81.5°F

The warmest month (with the highest average high temperature) is August (82.6°F).
The month with the lowest average high temperature is December (64.2°F).

  • Average low temperature in September: 64.4°F

The month with the highest average low temperature is August (65.8°F).
The coldest month (with the lowest average low temperature) is February (48.7°F).

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Average pressure in September
La Mesa, CA

Average pressure in September - La Mesa, CA
  • Average pressure in September: 29.88"

The month with the highest atmospheric pressure is January (30.09").
The month with the lowest atmospheric pressure is June (29.87").

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Average wind speed in September
La Mesa, CA

Average wind speed in September - La Mesa, CA
  • Average wind speed in September: 4.7mph

The windiest month (with the highest average wind speed) is April (5.7mph).
The calmest month (with the lowest average wind speed) is October (4.5mph).

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Average humidity in September
La Mesa, CA

Average humidity in September - La Mesa, CA
  • Average humidity in September: 61%

The month with the highest relative humidity is May (68%).
The month with the lowest relative humidity is November (55%).

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Average rainfall in September
La Mesa, CA

Average rainfall in September - La Mesa, CA
  • Average rainfall in September: 0.28"

The wettest month (with the highest rainfall) is February (1.3").
The driest month (with the least rainfall) is June (0.08").

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Average rainfall days in September
La Mesa, CA

Average rainfall days in September - La Mesa, CA
  • Average rainfall days in September: 3.7 days

The month with the highest number of rainy days is March (7.8 days).
The month with the least rainy days is June (1.4 days).

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Average daylight in September /
Average sunshine in September
La Mesa, CA

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

The month with the longest days is June (Average daylight: 14.3h).
The month with the shortest days is December (Average daylight: 10h).

  • Average sunshine in September: 10.3h

The month with the most sunshine is July (Average sunshine: 12h).
The month with the least sunshine is December (Average sunshine: 6.7h).

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Average sunshine days in September
La Mesa, CA

Average sunshine days in September - La Mesa, CA
  • Average sunshine days in September: 24.6 days

The month with the most sunshine days is June (28.1 days).
The month with the least sunshine days is February (21 days).

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Average UV index in September
La Mesa, CA

Average UV index in September - La Mesa, CA
  • Average UV index in September: 6

Months with the highest UV index are June, July, August and September (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 4).

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Average cloud cover in September
La Mesa, CA

Average cloud cover in September - La Mesa, CA
  • Average cloud cover in September: 11

The month with the most cloud cover is March (Cloud cover 24).
The month with the least cloud cover is August (Cloud cover 8).

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Average visibility in September
La Mesa, CA

Average visibility in September - La Mesa, 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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