September weather forecastPortola Hills, CA
September
Weather in September
The first month of the autumn, September, is still a warm month in Portola Hills, California, with an average temperature varying between 63.7°F (17.6°C) and 81°F (27.2°C).Temperature
In the transition from August to September, Portola Hills reports an average high-temperature of a still moderately hot 81°F (27.2°C), indicating a close resemblance to the prior month. During September nights, Portola Hills records an average temperature of 63.7°F (17.6°C).Heat index
In September, the average heat index is appraised at 82.4°F (28°C). Extended exposure and activity might lead to tiredness, potentially resulting in heat cramps.Note that heat index values are valued for light wind and location in the shade. Direct sunshine exposure could raise heat index values by as much as 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'real feel', melds the effects of warmth and moisture to generate a feeling of heat. This effect is personal, influenced by the individual's physical activity and heat sensitivity, shaped by factors including wind, attire, and metabolic variations. Take note that direct exposure to the sun can increase the felt temperature, possibly adding 15 Fahrenheit (8 Celsius) degrees to the heat index. Heat index values hold particular importance for children. Youngsters are usually more at risk than adults, considering they sweat less. Additionally, their high skin surface area compared to their little bodies and their high heat production due to activity increases their risk.
Humidity
In Portola Hills, the average relative humidity in September is 61%.Rainfall
In September, the rain falls for 4.6 days. Throughout September, 0.31" (8mm) of precipitation is accumulated. Throughout the year, there are 65.4 rainfall days, and 9.17" (233mm) of precipitation is accumulated.Daylight
In Portola Hills, the average length of the day in September is 12h and 22min.On the first day of the month, sunrise is at 6:24 am and sunset at 7:15 pm. On the last day of September, sunrise is at 6:44 am and sunset at 6:35 pm PDT.
Sunshine
The average sunshine in September in Portola Hills is 10.6h.UV index
June through September, with an average maximum UV index of 6, are months with the highest UV index. A UV Index value of 6 to 7 symbolizes a high health vulnerability from exposure to the Sun's UV radiation for the average person.Note: In September, the average maximum UV index of 6 translates into the following recommendations:
Take precautions and utilize sun safety practices. Protection against skin and eye damage is required. During the period from 10 a.m. to 4 p.m., UV radiation is highest. Try to avoid direct sunlight during these hours. Enhance your sun protection with tightly woven, yet airy clothing.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Portola Hills, CA
- Average high temperature in September: 81°F
The warmest month (with the highest average high temperature) is August (82°F).
The month with the lowest average high temperature is December (63.1°F).
- Average low temperature in September: 63.7°F
The month with the highest average low temperature is August (64.4°F).
The coldest month (with the lowest average low temperature) is February (48.7°F).
Average pressure in September
Portola Hills, CA
- Average pressure in September: 29.88"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are June and September (29.88"Hg).
Average wind speed in September
Portola Hills, CA
- Average wind speed in September: 4.5mph
The windiest months (with the highest average wind speed) are April and May (5.7mph).
The calmest months (with the lowest average wind speed) are August and September (4.5mph).
Average humidity in September
Portola Hills, CA
- Average humidity in September: 61%
The months with the highest relative humidity are May and June (69%).
The month with the lowest relative humidity is November (55%).
Average rainfall in September
Portola Hills, CA
- Average rainfall in September: 0.31"
The wettest month (with the highest rainfall) is December (1.85").
The driest month (with the least rainfall) is June (0.08").
Average rainfall days in September
Portola Hills, CA
- Average rainfall days in September: 4.6 days
The month with the highest number of rainy days is March (8.1 days).
The month with the least rainy days is June (2 days).
Average daylight in September /
Average sunshine in September
Portola Hills, CA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 10h and 0min).
- Average sunshine in September: 10h and 36min
The months with the most sunshine are July and August (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 6h and 36min).
Average sunshine days in September
Portola Hills, CA
- Average sunshine days in September: 21.8 days
The months with the most sunshine days are January and October (24.2 days).
The month with the least sunshine days is May (19.3 days).
Average UV index in September
Portola Hills, CA
- Average UV index in September: 6
The months with the highest UV index are June, July, August and September (UV index 6).
The months with the lowest UV index are January, February, March, November and December (UV index 4).
Average cloud cover in September
Portola Hills, CA
- Average cloud cover in September: 10
The months with the most cloud cover are March and December (Cloud cover 24).
The month with the least cloud cover is August (Cloud cover 6).
Average visibility in September
Portola Hills, 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).
