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 highest point of temperatures in San Mateo falls in August and September, when the average high-temperature ascends to 71.2°F (21.8°C).Humidity
The average relative humidity in September in San Mateo is 72%.Rainfall
Months with rainfall in San Mateo, California, are January through May, September through December. September is the first month it rains in San Mateo. 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
The average length of the day in September in San Mateo is 12h and 25min.On the first day of September in San Mateo, 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
In September, the average sunshine is 11h.UV index
June through September, with an average maximum UV index of 5, are months with the highest UV index in San Mateo, California. A UV Index estimate of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for the average person.Note: The UV index of 5 in September translates into these instructions:
Be careful. Light complexion individuals might get burns in fewer than 30 minutes. The Sun is at its harshest during midday; protect yourself by staying in shaded areas and minimizing exposure. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays.
Frequently asked questions
What is the hottest time of year in San Mateo?
What are September temperatures in San Mateo?
What is the average humidity in September in San Mateo?
When does it start to rain in San Mateo?
How many hours of daylight does San Mateo have in September?
When are sunrise and sunset in September in San Mateo?
How many hours of sunshine does San Mateo have in September?
When is the highest UV index in San Mateo?
What is the UV index intensity in September in San Mateo?
Average temperature in September
San Mateo, 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
San Mateo, 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 Mateo, 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
San Mateo, 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
San Mateo, 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
San Mateo, 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
San Mateo, 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
San Mateo, 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
San Mateo, 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
San Mateo, 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
San Mateo, 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).
San Mateo, California, USA
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