September weather forecast
Rosemont, CA

Weather in September

September, the first month of the autumn, in Rosemont, is also a hot month, with average temperature ranging between min 58.8°F (14.9°C) and max 88.3°F (31.3°C).

Temperature

In Rosemont, the average high-temperature in September is practically the same as in August - a still tropical 88.3°F (31.3°C). In Rosemont, the average low-temperature is 58.8°F (14.9°C).

Heat index

The average heat index is estimated at a hot 89.6°F (32°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 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', 'felt air temperature', 'apparent temperature', or 'feels like', combines air temperature and relative humidity to represent a human perceived temperature equivalent. Additional factors like metabolic differences, differences in body mass, height, and shape, pregnancy, and activity influence one's weather impression. Be aware that direct exposure to sunlight increases heat impact and may raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Children are often less aware of the need to rest and re-hydrate. Thirst is a late sign of dehydration - it is vital to remain hydrated, particularly during prolonged physical activities.

Humidity

July and September, with an average relative humidity of 44%, are the least humid months in Rosemont.

Rainfall

In Rosemont, in September, it is raining for 2.1 days, with typically 0.16" (4mm) of accumulated precipitation. Throughout the year, in Rosemont, California, there are 70.5 rainfall days, and 15.04" (382mm) of precipitation is accumulated.

Daylight

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

Sunshine

In Rosemont, the average sunshine is 11.2h.

UV index

The average daily maximum UV index is 5. A UV Index value of 3 to 5 symbolizes a moderate threat to health from unsafe exposure to the UV radiation for the average person.
Note: In September, the average maximum UV index of 5 translate into the following recommendations:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
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FAQ

What is the temperature in September in Rosemont?

In Rosemont, in September, the average high-temperature is 88.3°F (31.3°C), and the average low-temperature is 58.8°F (14.9°C). In September, the average heat index (a.k.a. 'apparent temperature', 'real feel'), which takes the relative humidity and factors it into the air temperature reading, is estimated at 89.6°F (32°C).

What is the least humid month in Rosemont?

Months with the lowest humidity are July and September, with an average relative humidity of 44%.

What is the average humidity in September in Rosemont?

The average relative humidity in September in Rosemont is 44%.

How much does it rain in Rosemont in September?

In Rosemont, during September, the rain falls for 2.1 days and regularly aggregates up to 0.16" (4mm) of precipitation.

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

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

How many hours of sunshine does Rosemont have in September?

In September, the average sunshine is 11.2h.

What is the UV index reading in September in Rosemont?

In September, the average daily maximum UV index in Rosemont 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
Rosemont, CA

Average temperature in September - Rosemont, CA
  • Average high temperature in September: 88.3°F

The warmest month (with the highest average high temperature) is July (94.5°F).
The month with the lowest average high temperature is December (54.3°F).

  • Average low temperature in September: 58.8°F

The month with the highest average low temperature is August (59.9°F).
The coldest months (with the lowest average low temperature) are January and December (40.8°F).

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Average pressure in September
Rosemont, CA

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

The month with the highest atmospheric pressure is January (30.15").
The month with the lowest atmospheric pressure is June (29.9").

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Average wind speed in September
Rosemont, CA

Average wind speed in September - Rosemont, CA
  • Average wind speed in September: 4.1mph

The windiest month (with the highest average wind speed) is February (5.7mph).
The calmest month (with the lowest average wind speed) is September (4.1mph).

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Average humidity in September
Rosemont, CA

Average humidity in September - Rosemont, CA
  • Average humidity in September: 44%

The month with the highest relative humidity is March (75%).
Months with the lowest relative humidity are July and September (44%).

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Average rainfall in September
Rosemont, CA

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

The wettest month (with the highest rainfall) is March (2.72").
The driest months (with the least rainfall) are July and August (0.04").

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Average rainfall days in September
Rosemont, CA

Average rainfall days in September - Rosemont, CA
  • Average rainfall days in September: 2.1 days

The month with the highest number of rainy days is March (12.6 days).
The month with the least rainy days is July (1 days).

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

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

The month with the longest days is June (Average daylight: 14.8h).
The month with the shortest days is December (Average daylight: 9.5h).

  • Average sunshine in September: 11.2h

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

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Average sunshine days in September
Rosemont, CA

Average sunshine days in September - Rosemont, CA
  • Average sunshine days in September: 27.5 days

The month with the most sunshine days is July (29.7 days).
The month with the least sunshine days is March (17.6 days).

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Average UV index in September
Rosemont, CA

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

Months with the highest UV index are June and July (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
Rosemont, CA

Average cloud cover in September - Rosemont, CA
  • Average cloud cover in September: 8

The month with the most cloud cover is March (Cloud cover 38).
The month with the least cloud cover is July (Cloud cover 4).

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Average visibility in September
Rosemont, CA

Average visibility in September - Rosemont, 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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