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 snowfall in September
- Average snowfall 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
In Portola, the beginning of September is marked by a marginally lowered average high-temperature, shifting from August's 81.1°F (27.3°C) to a still moderately hot 73.8°F (23.2°C). Portola records a consistent low-temperature average of 42.3°F (5.7°C) during September, indicating a significant difference from the daytime heat.Humidity
In Portola, the average relative humidity in September is 46%.Rainfall
In Portola, in September, during 4.5 rainfall days, 0.43" (11mm) of precipitation is typically accumulated. In Portola, during the entire year, the rain falls for 80.1 days and collects up to 22.95" (583mm) of precipitation.Snowfall
January through June, September through December are months with snowfall. September is the first month it typically snows in Portola. Throughout September, in the average 0.4 snowfall days, it receives 1.02" (26mm) of snow. Throughout the year, there are 69.3 snowfall days, and 103.5" (2629mm) of snow is accumulated.Daylight
The average length of the day in September is 12h and 26min.On the first day of September, sunrise is at 6:30 am and sunset at 7:32 pm. On the last day of the month, sunrise is at 6:57 am and sunset at 6:45 pm PDT.
Sunshine
The average sunshine in September is 11h.UV index
In Portola, the average daily maximum UV index in September is 3. A UV Index value of 3 to 5 symbolizes a medium health hazard from unprotected exposure to Sun's UV rays for average individuals.Note: In September, the maximum UV index of 3 translates into these guidelines:
Take precautions - Protection against sunburn is recommended. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. To best shield against UV radiation, choose sun-safe garments and dependable sunglasses. Be alert to the fact! The reflection from snow can nearly double the UV radiation of the Sun.
Frequently asked questions
What is the average September temperature in Portola?
What is the average humidity in September in Portola?
How many days does it rain in September in Portola?
When does it start to snow in Portola?
What is the average length of the day in September in Portola?
What time are sunrise and sunset in September in Portola?
How many hours of sunshine does Portola have in September?
What is the UV index intensity in September in Portola?
Average temperature in September
Portola, CA
- Average high temperature in September: 73.8°F
The warmest month (with the highest average high temperature) is July (82.9°F).
The month with the lowest average high temperature is December (37.2°F).
- Average low temperature in September: 42.3°F
The month with the highest average low temperature is July (47.5°F).
The coldest month (with the lowest average low temperature) is December (21.6°F).
Average pressure in September
Portola, CA
- Average pressure in September: 29.93"Hg
The month with the highest atmospheric pressure is January (30.19"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).
Average wind speed in September
Portola, CA
- Average wind speed in September: 5.2mph
The windiest month (with the highest average wind speed) is March (6.6mph).
The calmest months (with the lowest average wind speed) are August and September (5.2mph).
Average humidity in September
Portola, CA
- Average humidity in September: 46%
The months with the highest relative humidity are January and March (81%).
The months with the lowest relative humidity are July and August (40%).
Average rainfall in September
Portola, CA
- Average rainfall in September: 0.43"
The wettest month (with the highest rainfall) is March (4.02").
The driest month (with the least rainfall) is August (0.2").
Average rainfall days in September
Portola, CA
- Average rainfall days in September: 4.5 days
The month with the highest number of rainy days is May (11.8 days).
The month with the least rainy days is July (3.3 days).
Average snowfall in September
Portola, CA
- Average snowfall in September: 1.02"
The month with the highest snowfall is December (22.52").
The months with the least snowfall are July and August (0").
Average snowfall days in September
Portola, CA
- Average snowfall days in September: 0.4 days
The month with the highest number of snowfall days is March (14.7 days).
The months with the least snowfall days are July and August (0 days).
Average daylight in September /
Average sunshine in September
Portola, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in September: 11h
The month with the most sunshine is July (Average sunshine: 12h).
The month with the least sunshine is January (Average sunshine: 5h).
Average sunshine days in September
Portola, CA
- Average sunshine days in September: 25 days
The month with the most sunshine days is August (26 days).
The month with the least sunshine days is March (11.8 days).
Average UV index in September
Portola, CA
- Average UV index in September: 3
The months with the highest UV index are June, July and August (UV index 5).
The month with the lowest UV index is November (UV index 1).
Average cloud cover in September
Portola, CA
- Average cloud cover in September: 12
The month with the most cloud cover is March (Cloud cover 47).
The month with the least cloud cover is July (Cloud cover 7).
Average visibility in September
Portola, CA
- Average visibility in September: 6mi
The months with the highest visibility are May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January and December (4mi).
Portola, California, USA
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