September weather forecast
Pomona, CA

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Trails in the rural mountainous region of Pomona, California, with scenic slopes and dense population down below
Trails in the rural mountainous region of Pomona, California, with scenic slopes and dense population down below

Weather in September

With the advent of September, Pomona begins its gradual departure from the grips of summer. Temperatures experience a slight dip making cool breezes a common part of the daily weather. Outdoor activities under the diminishing daylight hours become more comfortable thanks to the step down from the blistering summer heat. A tinge of increased cloud cover adds to the contrasting weather patterns of September. As leaves start changing their colors, Pomona prepares to welcome the vibrant shades of autumn.

Temperature

As Pomona steps into September, the average high-temperature holds at a still hot 87.6°F (30.9°C), hinting at a minor fluctuation from the prior month. Despite a noticeable differential from daytime highs, Pomona notes an average nighttime low-temperature of 64°F (17.8°C) in September.

Heat index

For September, the heat index is evaluated at a tropical 89.6°F (32°C). Remaining active during long-lasting exposure could cause fatigue, leading to heat cramps.
The metrics for the heat index are tailored for both shady environments and light winds. The heat index could experience an increase of 15 Fahrenheit (8 Celsius) degrees due to direct sunlight.
Note: The heat index, also known as 'apparent temperature' or 'felt air temperature', offers an insight into how hot it feels when we factor in moisture content. Factors such as metabolic variation, pregnancy, and physical activity play a role in one's impression of weather. Given direct exposure to sunlight, one might experience a rise in the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly important for children. Children often lack awareness of the importance of taking breaks and rehydrating. The feeling of thirst is a late indication of dehydration, so maintaining hydration, especially during long periods of physical activity, is critical.

Humidity

In Pomona, the average relative humidity in September is 46%.

Rainfall

In September, in Pomona, the rain falls for 2.5 days. Throughout September, 0.08" (2mm) of precipitation is accumulated. In Pomona, during the entire year, the rain falls for 48 days and collects up to 7.52" (191mm) of precipitation.

Snowfall

January, March through December are months without snowfall in Pomona, California.

Daylight

In September, the average length of the day in Pomona is 12h and 22min.
On the first day of September in Pomona, sunrise is at 6:25 am and sunset at 7:16 pm. On the last day of the month, sunrise is at 6:45 am and sunset at 6:36 pm PDT.

Sunshine

In Pomona, the average sunshine in September is 10.8h.

UV index

The average daily maximum UV index in September in Pomona is 6. A UV Index estimate of 6 to 7 represents a high threat to health from exposure to the Sun's UV radiation for the ordinary person.
Note: A daily maximum UV index of 6 in September translates into the following instructions:
Enforce precautions and stick to sun safety measures. Preservation from skin and eye damage is essential. The Sun's UV radiation is at its strongest between the hours of 10 a.m. and 4 p.m. Minimize direct exposure to the sun during this period. To cut down UV radiation exposure by about half, sport a wide-brim hat.

Frequently asked questions

Is it hot in Pomona during September?

The high-temperature during September is 87.6°F (30.9°C) and the low-temperature is 64°F (17.8°C). The average heat index (a.k.a. 'real feel', 'felt air temperature'), which represents the influence of relative humidity on air temperature, in September is evaluated at 89.6°F (32°C).

What is the average humidity in September in Pomona?

In September, the average relative humidity is 46%.

How many days does it rain in September in Pomona?

In Pomona, California, in September, during 2.5 rainfall days, 0.08" (2mm) of precipitation is typically accumulated.

When it does not snow in Pomona?

January, March through December are months without snowfall.

How many hours of daylight does Pomona have in September?

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

When is the sunrise / sunset in September in Pomona?

On the first day of September in Pomona, sunrise is at 6:25 am and sunset at 7:16 pm. On the last day of the month, sunrise is at 6:45 am and sunset at 6:36 pm PDT.

How long on average sun shines in September in Pomona?

The average sunshine duration in September in Pomona is 10.8h.

What is the UV index intensity in September in Pomona?

In Pomona, the average daily maximum UV index in September is 6. A UV Index reading of 6 to 7 represents a high health threat from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Pomona, CA

Average temperature in September - Pomona, CA
  • Average high temperature in September: 87.6°F

The warmest month (with the highest average high temperature) is August (90.1°F).
The month with the lowest average high temperature is December (63.1°F).

  • Average low temperature in September: 64°F

The month with the highest average low temperature is August (65.7°F).
The coldest months (with the lowest average low temperature) are February and December (46.8°F).

Average pressure in September
Pomona, CA

Average pressure in September - Pomona, CA
  • Average pressure in September: 29.88"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is June (29.87"Hg).

Average wind speed in September
Pomona, CA

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

The windiest months (with the highest average wind speed) are April and May (5.7mph).
The calmest month (with the lowest average wind speed) is September (4.4mph).

Average humidity in September
Pomona, CA

Average humidity in September - Pomona, CA
  • Average humidity in September: 46%

The month with the highest relative humidity is May (56%).
The months with the lowest relative humidity are August and November (45%).

Average rainfall in September
Pomona, CA

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

The wettest months (with the highest rainfall) are February and December (1.65").
The driest months (with the least rainfall) are June and August (0.04").

Average rainfall days in September
Pomona, CA

Average rainfall days in September - Pomona, CA
  • Average rainfall days in September: 2.5 days

The month with the highest number of rainy days is March (7.6 days).
The month with the least rainy days is June (0.8 days).

Average snowfall days in September
Pomona, CA

Average snowfall days in September - Pomona, CA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (0.1 days).
The months with the least snowfall days are January, March, April, May, June, July, August, September, October, November and December (0 days).

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

Average daylight in September / Average sunshine in September - Pomona, 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 month with the most sunshine is July (Average sunshine: 12h and 12min).
The months with the least sunshine are February and December (Average sunshine: 6h and 54min).

Average sunshine days in September
Pomona, CA

Average sunshine days in September - Pomona, CA
  • Average sunshine days in September: 26.5 days

The month with the most sunshine days is June (28.7 days).
The month with the least sunshine days is February (21.1 days).

Average UV index in September
Pomona, CA

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

The month with the highest UV index is August (UV index 7).
The months with the lowest UV index are January, February, November and December (UV index 4).

Average cloud cover in September
Pomona, CA

Average cloud cover in September - Pomona, CA
  • Average cloud cover in September: 7

The months with the most cloud cover are February, March and December (Cloud cover 21).
The month with the least cloud cover is August (Cloud cover 4).

Average visibility in September
Pomona, CA

Average visibility in September - Pomona, 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).

Pomona, California, USA

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