September weather forecast
Pasadena, CA

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Pasadena City Hall in California, with neon-lit paths and natural gardens, under a perfect blue night sky
Pasadena City Hall in California, with neon-lit paths and natural gardens, under a perfect blue night sky

Weather in September

September squeezes the summer in Pasadena a bit more, maintaining an average high temperature of 84.4°F (29.1°C). As the year progresses towards its end, the weather in September stays relatively warm but introduces the onset of cooler nights. Despite the slight drop in temperature, the ample sunshine ensures a bright and vibrant atmosphere. The headway into autumn does not deter outdoor activities, allowing residents and visitors to continue soaking the sun. September holds onto the remnants of summer, giving Pasadena one last full month of sunshine and warmth before easing into fall.

Temperature

With the arrival of September, Pasadena's average high-temperature registers at a warm 84.4°F (29.1°C), indicating a subtle variation from the previous month. An average low-temperature of 63.3°F (17.4°C) is observed during September nights.

Heat index

The heat index value for September is calculated to be a hot 86°F (30°C). If one persists in activity during exposure, it could induce weariness and subsequently, heat cramps.
The heat index's values are generally associated with conditions in shade and light breezes. With exposure to direct sunshine, the heat index could climb by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature' or 'real feel', is an index that combines air temperature and relative humidity to determine the human-perceived temperature equivalent. A person's impression of weather can be shaped by many aspects, among them metabolic variations, pregnancy, and levels of physical activity. It is noteworthy that being in direct sunlight can enhance the weather's impact, raising the heat index by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for babies and toddlers. Youngsters frequently overlook the need for breaks and fluid intake. Thirst is an advanced sign of dehydration - thereby highlighting the importance of keeping hydrated, particularly during long physical activities.

Humidity

In September, the average relative humidity is 50%.

Rainfall

In Pasadena, in September, during 2.6 rainfall days, 0.16" (4mm) of precipitation is typically accumulated. Throughout the year, in Pasadena, there are 50.1 rainfall days, and 8.5" (216mm) of precipitation is accumulated.

Daylight

In September, the average length of the day is 12h and 22min.
On the first day of September, sunrise is at 6:26 am and sunset at 7:17 pm. On the last day of the month, sunrise is at 6:46 am and sunset at 6:37 pm PDT.

Sunshine

In Pasadena, California, the average sunshine in September is 10.8h.

UV index

June through September, with an average maximum UV index of 6, are months with the highest UV index in Pasadena. A UV Index of 6 to 7 symbolizes a high health risk from unprotected exposure to Sun's UV rays for average individuals.
Note: A maximum daily UV index of 6 during September morphs into the following directions:
Eschew overexposure. Those with light skin may suffer burns in fewer than 20 minutes. Stay in the shade and limit direct sun exposure between 10 a.m. and 4 p.m., when UV radiation is at its strongest. Remember, however, that not all shade structures provide full sun protection. In bright sunlight, prioritize sunglasses that grant protection from UVA and UVB radiation.
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Frequently asked questions

Is it hot in Pasadena during September?

The average high-temperature and low-temperature in Pasadena, California, during September are 84.4°F (29.1°C) and 63.3°F (17.4°C) respectively. The average heat index (a.k.a. 'felt air temperature', 'apparent temperature'), which calculates the temperature value influenced by the moisture in the air, in September is calculated to be 86°F (30°C).

What is the average humidity in September in Pasadena?

In September, the average relative humidity is 50%.

How many days does it rain in September in Pasadena?

In Pasadena, in September, it is raining for 2.6 days, with typically 0.16" (4mm) of accumulated precipitation.

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

In Pasadena, the average day length in September is 12h and 22min.

When are sunrise and sunset in September in Pasadena?

On the first day of September, sunrise is at 6:26 am and sunset at 7:17 pm. On the last day of the month, sunrise is at 6:46 am and sunset at 6:37 pm PDT.

How long on average sun shines in September in Pasadena?

In September, the average sunshine duration in Pasadena is 10.8h.

When is the highest UV index in Pasadena?

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

What is the UV index intensity in September in Pasadena?

The average daily maximum UV index in September in Pasadena, California, is 6. A UV Index value of 6 to 7 symbolizes a high health vulnerability from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Pasadena, CA

Average temperature in September - Pasadena, CA
  • Average high temperature in September: 84.4°F

The warmest month (with the highest average high temperature) is August (87.1°F).
The month with the lowest average high temperature is December (61.7°F).

  • Average low temperature in September: 63.3°F

The month with the highest average low temperature is August (64.9°F).
The coldest month (with the lowest average low temperature) is February (46.6°F).

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Average pressure in September
Pasadena, CA

Average pressure in September - Pasadena, CA
  • Average pressure in September: 29.89"Hg

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

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Average wind speed in September
Pasadena, CA

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

The windiest month (with the highest average wind speed) is April (5.8mph).
The calmest month (with the lowest average wind speed) is September (4.4mph).

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Average humidity in September
Pasadena, CA

Average humidity in September - Pasadena, CA
  • Average humidity in September: 50%

The month with the highest relative humidity is June (58%).
The month with the lowest relative humidity is November (47%).

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Average rainfall in September
Pasadena, CA

Average rainfall in September - Pasadena, CA
  • Average rainfall in September: 0.16"

The wettest month (with the highest rainfall) is February (1.77").
The driest month (with the least rainfall) is June (0.04").

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Average rainfall days in September
Pasadena, CA

Average rainfall days in September - Pasadena, CA
  • Average rainfall days in September: 2.6 days

The month with the highest number of rainy days is March (7.8 days).
The month with the least rainy days is June (1.1 days).

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

Average daylight in September / Average sunshine in September - Pasadena, CA
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 9h and 54min).

  • Average sunshine in September: 10h and 5min

The months with the most sunshine are June and July (Average sunshine: 12h and 6min).
The months with the least sunshine are January, February and December (Average sunshine: 6h and 54min).

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Average sunshine days in September
Pasadena, CA

Average sunshine days in September - Pasadena, CA
  • Average sunshine days in September: 25.2 days

The month with the most sunshine days is June (27.5 days).
The month with the least sunshine days is February (21.5 days).

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Average UV index in September
Pasadena, CA

Average UV index in September - Pasadena, CA
  • Average UV index in September: 6

The 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
Pasadena, CA

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

The months with the most cloud cover are March and December (Cloud cover 21).
The month with the least cloud cover is August (Cloud cover 5).

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Average visibility in September
Pasadena, CA

Average visibility in September - Pasadena, CA
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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Pasadena, California, USA

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