Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
The shift from August to September coincides with a small decrease in the average high-temperature, down to a hot 90.9°F (32.7°C) from a very hot 96.4°F (35.8°C). Riverdale Park experiences a significant downturn from peak daytime temperatures throughout September, with the average low-temperature dipping to a mild 59.9°F (15.5°C).Heat index
The heat index for September is estimated at a tropical 93.2°F (34°C). Adopt heightened safety measures, heat cramps and heat exhaustion may occur. Sustained activity might cause heatstroke.It is essential to grasp that the heat index's numbers are for shade and light wind settings. Heat index values can rise by 15 Fahrenheit (8 Celsius) degrees when in direct sunlight.
Note: The heat index, also known as 'real feel' or 'felt air temperature', binds temperature metrics with humidity values to give a sense of the actual warmth. The impression of weather on a person can be swayed by additional aspects, including metabolic variations, pregnancy, and activity levels. Given the impact of direct sunlight, it's noteworthy that the felt temperature can rise by 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for children. Youths are typically more endangered than adults since they usually sweat less. Their larger skin surface concerning their smaller bodies and higher heat production due to activity further adds to their vulnerability.
Humidity
In September, the average relative humidity is 41%.Rainfall
In Riverdale Park, in September, it is raining for 1.6 days, with typically 0.08" (2mm) of accumulated precipitation. Throughout the year, there are 54.3 rainfall days, and 6.54" (166mm) of precipitation is accumulated.Daylight
In September, the average length of the day is 12h and 25min.On the first day of September, sunrise is at 6:35 am and sunset at 7:32 pm. On the last day of the month, sunrise is at 6:59 am and sunset at 6:48 pm PDT.
Sunshine
The average sunshine in September is 11.5h.UV index
In Riverdale Park, the average daily maximum UV index in September is 6. A UV Index value of 6 to 7 symbolizes a high health risk from unprotected exposure to Sun's UV rays for the average person.Note: A daily high UV index of 6 in September leads to these guidelines:
Embrace precautions and observe sun safety norms. Evasion of sunburn is a necessity. The hours from 10 a.m. to 4 p.m. have the most intense UV radiation. As much as possible, limit direct sun exposure during this period. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How hot is it in September?
What is the average humidity in September?
How many days does it rain in September?
What is the average length of the day in September?
When is the sunrise / sunset in September in Riverdale Park?
How many hours of sunshine does Riverdale Park have in September?
How high is the UV index in September?
Average temperature in September
Riverdale Park, CA
- Average high temperature in September: 90.9°F
The warmest month (with the highest average high temperature) is July (97.7°F).
The month with the lowest average high temperature is December (55.6°F).
- Average low temperature in September: 59.9°F
The month with the highest average low temperature is July (62.1°F).
The coldest months (with the lowest average low temperature) are January and December (41.9°F).
Average pressure in September
Riverdale Park, CA
- Average pressure in September: 29.93"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
Riverdale Park, CA
- Average wind speed in September: 5.8mph
The windiest month (with the highest average wind speed) is June (7.3mph).
The calmest month (with the lowest average wind speed) is November (5.2mph).
Average humidity in September
Riverdale Park, CA
- Average humidity in September: 41%
The month with the highest relative humidity is January (72%).
The month with the lowest relative humidity is July (37%).
Average rainfall in September
Riverdale Park, CA
- Average rainfall in September: 0.08"
The wettest month (with the highest rainfall) is March (1.3").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in September
Riverdale Park, CA
- Average rainfall days in September: 1.6 days
The month with the highest number of rainy days is March (10.3 days).
The month with the least rainy days is August (0.9 days).
Average daylight in September /
Average sunshine in September
Riverdale Park, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in September: 11h and 3min
The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 6h and 0min).
Average sunshine days in September
Riverdale Park, CA
- Average sunshine days in September: 27.1 days
The month with the most sunshine days is August (29.2 days).
The month with the least sunshine days is March (19.6 days).
Average UV index in September
Riverdale Park, CA
- Average UV index in September: 6
The months with the highest UV index are June, July and August (UV index 7).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in September
Riverdale Park, CA
- Average cloud cover in September: 6
The month with the most cloud cover is March (Cloud cover 33).
The month with the least cloud cover is July (Cloud cover 4).
Average visibility in September
Riverdale Park, 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).
Riverdale Park, California, USA
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