September weather forecastMountain View, CA
September
Weather in September
The first month of the autumn, September, is still a warm month in Mountain View, California, with an average temperature fluctuating between 56.1°F (13.4°C) and 77.9°F (25.5°C).Temperature
September brings a marginal elevation to a still moderately hot 77.9°F (25.5°C) from August's 79.3°F (26.3°C) in Mountain View's average high-temperatures. In September, the temperature sees a substantial plunge from daytime highs to a low average of 56.1°F (13.4°C).Humidity
The months with the lowest humidity are July, September and October, with an average relative humidity of 63%.Rainfall
In September, the rain falls for 2.3 days. Throughout September, 0.08" (2mm) of precipitation is accumulated. In Mountain View, during the entire year, the rain falls for 53.1 days and collects up to 4.41" (112mm) of precipitation.Daylight
In Mountain View, the average length of the day in September is 12h and 25min.On the first day of the month, sunrise is at 6:39 am and sunset at 7:36 pm. On the last day of September, sunrise is at 7:03 am and sunset at 6:52 pm PDT.
Sunshine
The average sunshine in September is 11h.UV index
The average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a medium health hazard from exposure to the Sun's UV radiation for average individuals.Note: The maximum daily UV index of 5 in September converts into the following recommendations:
Exercise care. People with light skin might get burns in fewer than 30 minutes. Given the potency of the midday Sun's UV radiation, one should avoid prolonged exposure. Arm yourself against UV rays' harm with protective apparel and UV-filtering shades.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Mountain View, CA
- Average high temperature in September: 77.9°F
The warmest month (with the highest average high temperature) is July (79.7°F).
The month with the lowest average high temperature is December (56.5°F).
- Average low temperature in September: 56.1°F
The month with the highest average low temperature is August (56.8°F).
The coldest month (with the lowest average low temperature) is December (44.1°F).
Average pressure in September
Mountain View, 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 and September (29.92"Hg).
Average wind speed in September
Mountain View, CA
- Average wind speed in September: 4.7mph
The windiest months (with the highest average wind speed) are April and May (6.2mph).
The calmest months (with the lowest average wind speed) are August, September, October and November (4.7mph).
Average humidity in September
Mountain View, CA
- Average humidity in September: 63%
The month with the highest relative humidity is March (73%).
The months with the lowest relative humidity are July, September and October (63%).
Average rainfall in September
Mountain View, CA
- Average rainfall in September: 0.08"
The wettest months (with the highest rainfall) are February, March and December (0.83").
The driest months (with the least rainfall) are June, July and August (0.04").
Average rainfall days in September
Mountain View, CA
- Average rainfall days in September: 2.3 days
The month with the highest number of rainy days is March (10 days).
The month with the least rainy days is August (0.4 days).
Average daylight in September /
Average sunshine in September
Mountain View, 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 months with the most sunshine are July and August (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 5h and 54min).
Average sunshine days in September
Mountain View, CA
- Average sunshine days in September: 27.5 days
The months with the most sunshine days are July and August (29.8 days).
The month with the least sunshine days is March (19.4 days).
Average UV index in September
Mountain View, CA
- Average UV index in September: 5
The month with the highest UV index is June (UV index 6).
The months with the lowest UV index are February, November and December (UV index 3).
Average cloud cover in September
Mountain View, CA
- Average cloud cover in September: 11
The month with the most cloud cover is March (Cloud cover 35).
The month with the least cloud cover is July (Cloud cover 7).
Average visibility in September
Mountain View, 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).
