September weather forecastSan Bruno, CA
September
Weather in September
The first month of the autumn, September, is also an agreeable month in San Bruno, California, with an average temperature fluctuating between 69.8°F (21°C) and 56.5°F (13.6°C).Temperature
September is the warmest month, exhibiting average temperatures of 69.8°F (21°C) at the peak and 56.5°F (13.6°C) at the base.Humidity
The average relative humidity in September is 74%.Rainfall
In San Bruno, during September, the rain falls for 3.1 days and regularly aggregates up to 0.12" (3mm) of precipitation. Throughout the year, there are 81.8 rainfall days, and 13.46" (342mm) of precipitation is accumulated.Daylight
In San Bruno, the average length of the day in September is 12h and 25min.On the first day of September, sunrise is at 6:40 am and sunset at 7:38 pm. On the last day of the month, sunrise is at 7:05 am and sunset at 6:53 pm PDT.
Sunshine
The average sunshine in September is 10.8h.UV index
June through September, with an average maximum UV index of 5, are months with the highest UV index. A UV Index reading of 3 to 5 represents a moderate health risk from exposure to the Sun's UV rays for the average person.Note: A maximum high daily UV index of 5 during September translates into the following directions:
Make use of precautions - Shielding skin and eyes from injury is a requirement. Direct Sun exposure should be minimized especially during midday when radiation is most intense. In bright sunlight, prioritize sunglasses that grant protection from UVA and UVB radiation.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
San Bruno, CA
- Average high temperature in September: 69.8°F
The warmest month (with the highest average high temperature) is September (69.8°F).
The month with the lowest average high temperature is December (55.8°F).
- Average low temperature in September: 56.5°F
The month with the highest average low temperature is September (56.5°F).
The coldest month (with the lowest average low temperature) is December (47.7°F).
Average pressure in September
San Bruno, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is September (29.92"Hg).
Average wind speed in September
San Bruno, CA
- Average wind speed in September: 6.3mph
The windiest month (with the highest average wind speed) is April (8.5mph).
The calmest months (with the lowest average wind speed) are August and September (6.3mph).
Average humidity in September
San Bruno, CA
- Average humidity in September: 74%
The month with the highest relative humidity is August (79%).
The months with the lowest relative humidity are October and November (71%).
Average rainfall in September
San Bruno, CA
- Average rainfall in September: 0.12"
The wettest month (with the highest rainfall) is February (2.72").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in September
San Bruno, CA
- Average rainfall days in September: 3.1 days
The month with the highest number of rainy days is March (13.3 days).
The months with the least rainy days are July and August (2.2 days).
Average daylight in September /
Average sunshine in September
San Bruno, CA
- Average daylight in September: 12h and 24min
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: 10h and 48min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is December (Average sunshine: 5h and 48min).
Average sunshine days in September
San Bruno, CA
- Average sunshine days in September: 25.2 days
The month with the most sunshine days is July (27.3 days).
The month with the least sunshine days is March (16.3 days).
Average UV index in September
San Bruno, CA
- Average UV index in September: 5
The months with the highest UV index are June, July, August and September (UV index 5).
The months with the lowest UV index are February, November and December (UV index 3).
Average cloud cover in September
San Bruno, CA
- Average cloud cover in September: 16
The month with the most cloud cover is March (Cloud cover 37).
The month with the least cloud cover is September (Cloud cover 16).
Average visibility in September
San Bruno, 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).
