September weather forecastFoster City, CA
September
Weather in September
September, the first month of the autumn in Foster City, is still a pleasant month, with an average temperature ranging between min 56.7°F (13.7°C) and max 71.2°F (21.8°C).Temperature
The warmest months are August and September, with an average high-temperature of 71.2°F (21.8°C).Humidity
In September, the average relative humidity is 72%.Rainfall
January through May, September through December are months with rainfall. September is the first month it rains. Throughout September, in the average 0.9 rainfall days, it receives 0.04" (1mm) of precipitation. Throughout the year, there are 32.6 rainfall days, and 2.13" (54mm) of precipitation is accumulated.Daylight
In Foster City, 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 7:37 pm. On the last day of the month, sunrise is at 7:04 am and sunset at 6:53 pm PDT.
Sunshine
The average sunshine in September in Foster City is 11h.UV index
June through September, with an average maximum UV index of 5, are months with the highest UV index. A UV Index of 3 to 5 symbolizes a moderate health risk from unsafe exposure to UV radiation for the average person.Note: The maximum UV index of 5 during September leads to these instructions:
Take precautions - Protection against sunburn is recommended. Direct exposure to the Sun's intense radiation around midday should be avoided for health reasons. Sun protection is enhanced with clothing that boasts a tight weave yet offers a loose fit.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Foster City, CA
- Average high temperature in September: 71.2°F
The warmest months (with the highest average high temperature) are August and September (71.2°F).
The month with the lowest average high temperature is December (55.8°F).
- Average low temperature in September: 56.7°F
The month with the highest average low temperature is September (56.7°F).
The coldest month (with the lowest average low temperature) is January (46.9°F).
Average pressure in September
Foster City, 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
Foster City, CA
- Average wind speed in September: 5.9mph
The windiest month (with the highest average wind speed) is April (8mph).
The calmest months (with the lowest average wind speed) are August, September and October (5.9mph).
Average humidity in September
Foster City, CA
- Average humidity in September: 72%
The months with the highest relative humidity are March and August (76%).
The months with the lowest relative humidity are October and November (70%).
Average rainfall in September
Foster City, CA
- Average rainfall in September: 0.04"
The wettest month (with the highest rainfall) is February (0.55").
The driest months (with the least rainfall) are June, July and August (0").
Average rainfall days in September
Foster City, CA
- Average rainfall days in September: 0.9 days
The month with the highest number of rainy days is March (6.8 days).
The month with the least rainy days is July (0.3 days).
Average daylight in September /
Average sunshine in September
Foster City, 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: 11h and 0min
The month with the most sunshine is July (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 5h and 54min).
Average sunshine days in September
Foster City, CA
- Average sunshine days in September: 28.7 days
The month with the most sunshine days is July (30.4 days).
The month with the least sunshine days is February (23.3 days).
Average UV index in September
Foster City, 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 and December (UV index 3).
Average cloud cover in September
Foster City, CA
- Average cloud cover in September: 13
The month with the most cloud cover is March (Cloud cover 35).
The month with the least cloud cover is July (Cloud cover 11).
Average visibility in September
Foster City, 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).
