September weather forecastSan Geronimo, CA
September
Weather in September
September, the first month of the autumn in San Geronimo, is still a pleasant month, with an average temperature fluctuating between 70.9°F (21.6°C) and 56.3°F (13.5°C).Temperature
September temperatures tend to peak at an average high of 70.9°F (21.6°C) and dip to a low of 56.3°F (13.5°C).Humidity
In San Geronimo, the average relative humidity in September is 73%.Rainfall
In San Geronimo, California, during September, the rain falls for 3.4 days and regularly aggregates up to 0.12" (3mm) of precipitation. In San Geronimo, during the entire year, the rain falls for 80.3 days and collects up to 15.98" (406mm) of precipitation.Snowfall
In San Geronimo, snow does not fall in January through November.Daylight
In September, the average length of the day is 12h and 25min.On the first day of the month, sunrise is at 6:41 am and sunset at 7:39 pm. On the last day of September, in San Geronimo, sunrise is at 7:06 am and sunset at 6:54 pm PDT.
Sunshine
The average sunshine in September in San Geronimo is 10.5h.UV index
The months with the highest UV index in San Geronimo are June through September, with an average maximum UV index of 5. A UV Index reading of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV rays for the ordinary person.Note: In September, a daily maximum UV index of 5 leads to the following instructions:
Be mindful. Those with pale skin might receive burns in fewer than 30 minutes. Midday is when the Sun's radiation is strongest; avoid prolonged exposure during this time. For a sun-safe wardrobe, go for clothes that are tightly woven and generously sized.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
San Geronimo, CA
- Average high temperature in September: 70.9°F
The warmest month (with the highest average high temperature) is September (70.9°F).
The month with the lowest average high temperature is December (55.2°F).
- Average low temperature in September: 56.3°F
The month with the highest average low temperature is September (56.3°F).
The coldest month (with the lowest average low temperature) is December (46°F).
Average pressure in September
San Geronimo, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.92"Hg).
Average wind speed in September
San Geronimo, CA
- Average wind speed in September: 6.3mph
The windiest months (with the highest average wind speed) are April and May (8.3mph).
The calmest month (with the lowest average wind speed) is November (5.9mph).
Average humidity in September
San Geronimo, CA
- Average humidity in September: 73%
The month with the highest relative humidity is August (78%).
The month with the lowest relative humidity is October (69%).
Average rainfall in September
San Geronimo, CA
- Average rainfall in September: 0.12"
The wettest month (with the highest rainfall) is February (3.43").
The driest months (with the least rainfall) are July and August (0.08").
Average rainfall days in September
San Geronimo, CA
- Average rainfall days in September: 3.4 days
The month with the highest number of rainy days is March (12.8 days).
The month with the least rainy days is July (2.3 days).
Average snowfall days in September
San Geronimo, CA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is December (0.1 days).
The months with the least snowfall days are January, February, March, April, May, June, July, August, September, October and November (0 days).
Average daylight in September /
Average sunshine in September
San Geronimo, CA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in September: 10h and 30min
The month with the most sunshine is July (Average sunshine: 11h and 12min).
The month with the least sunshine is December (Average sunshine: 5h and 36min).
Average sunshine days in September
San Geronimo, CA
- Average sunshine days in September: 24.1 days
The months with the most sunshine days are June and July (24.8 days).
The month with the least sunshine days is March (16.6 days).
Average UV index in September
San Geronimo, 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 Geronimo, CA
- Average cloud cover in September: 19
The month with the most cloud cover is March (Cloud cover 39).
The month with the least cloud cover is September (Cloud cover 19).
Average visibility in September
San Geronimo, 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).
