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 yearly peak temperatures occur in August and September, averaging a high-temperature of 71.2°F (21.8°C).Humidity
In Foster City, the average relative humidity in September is 72%.Rainfall
Months with rainfall in Foster City, California, are January through May, September through December. September is the first month it rains in Foster City, California. Throughout September, in the average 0.9 rainfall days, it receives 0.04" (1mm) of precipitation. In Foster City, California, during the entire year, the rain falls for 32.6 days and collects up to 2.13" (54mm) of precipitation.Daylight
In September, the average length of the day is 12h and 25min.On the first day of the month, sunrise is at 6:40 am and sunset at 7:37 pm. On the last day of September, in Foster City, sunrise is at 7:04 am and sunset at 6:53 pm PDT.
Sunshine
In Foster City, the average sunshine in September is 11h.UV index
The months with the highest UV index in Foster City are June through September, with an average maximum UV index of 5. A UV Index of 3 to 5 symbolizes a moderate threat to health from unprotected exposure to Sun's UV rays for ordinary individuals.Note: A maximum daily UV index of 5 during September morphs into the following directions:
Be vigilant - A duty to shield skin and eyes from injury exists. For health reasons, it's advisable to reduce direct sun exposure during peak hours around midday. Experience reduced UV exposure by about half when donning a wide-brim hat.
Frequently asked questions
What time of the year is the hottest in Foster City?
What is the temperature in September in Foster City?
What is the average humidity in September in Foster City?
When does it start to rain in Foster City?
What is the average length of the day in September in Foster City?
What time are sunrise and sunset in September in Foster City?
How long on average sun shines in September in Foster City?
What is the month with the highest UV index in Foster City?
How high is the UV index in September in Foster City?
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 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 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).
Foster City, California, USA
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