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
September commences with an average high-temperature of a still warm 80.2°F (26.8°C), showing little deviation from August's 82.4°F (28°C). September nights see a notable contrast from daytime highs, with the nighttime temperature averaging at a mild 55.6°F (13.1°C).Humidity
In September, the average relative humidity is 59%.Rainfall
In Alviso, during September, the rain falls for 2.2 days and regularly aggregates up to 0.08" (2mm) of precipitation. Throughout the year, there are 52.8 rainfall days, and 4.06" (103mm) of precipitation is accumulated.Daylight
The average length of the day in September is 12h and 25min.On the first day of September, sunrise is at 6:39 am and sunset at 7:36 pm. On the last day of the month, sunrise is at 7:03 am and sunset at 6:51 pm PDT.
Sunshine
In Alviso, the average sunshine in September is 11.2h.UV index
In Alviso, the average daily maximum UV index in September is 5. A UV Index of 3 to 5 symbolizes a moderate health risk from unsafe exposure to UV radiation for the ordinary person.Note: The UV index of 5 during September translates into the following guidance:
Safety measures are advised. Light-skinned individuals may experience burns in under half an hour. Being exposed to the midday Sun can have harmful effects due to strong UV radiation; always take precautions. Tightly woven clothing, when worn loosely, shields effectively against the Sun.
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Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in Alviso in September?
What is the average humidity in September?
How much does it rain in September?
What is the average length of the day in September?
When is the sunrise / sunset in September?
How many hours of sunshine does Alviso have in September?
How high is the UV index in September?
Average temperature in September
Alviso, CA
- Average high temperature in September: 80.2°F
The warmest month (with the highest average high temperature) is July (83.5°F).
The month with the lowest average high temperature is December (56.3°F).
- Average low temperature in September: 55.6°F
The month with the highest average low temperature is August (56.8°F).
The coldest months (with the lowest average low temperature) are January and December (42.6°F).
Average pressure in September
Alviso, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.92"Hg).
Average wind speed in September
Alviso, CA
- Average wind speed in September: 4.4mph
The windiest month (with the highest average wind speed) is May (5.8mph).
The calmest months (with the lowest average wind speed) are October and November (4.3mph).
Average humidity in September
Alviso, CA
- Average humidity in September: 59%
The month with the highest relative humidity is March (73%).
The month with the lowest relative humidity is July (58%).
Average rainfall in September
Alviso, CA
- Average rainfall in September: 0.08"
The wettest month (with the highest rainfall) is March (0.83").
The driest months (with the least rainfall) are June, July and August (0.04").
Average rainfall days in September
Alviso, CA
- Average rainfall days in September: 2.2 days
The month with the highest number of rainy days is March (9.9 days).
The month with the least rainy days is August (0.4 days).
Average daylight in September /
Average sunshine in September
Alviso, 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 1min
The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 6h and 0min).
Average sunshine days in September
Alviso, CA
- Average sunshine days in September: 26.8 days
The month with the most sunshine days is August (29.6 days).
The month with the least sunshine days is March (19.5 days).
Average UV index in September
Alviso, CA
- Average UV index in September: 5
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in September
Alviso, CA
- Average cloud cover in September: 10
The month with the most cloud cover is March (Cloud cover 35).
The month with the least cloud cover is July (Cloud cover 5).
Average visibility in September
Alviso, 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).
Alviso, California, USA
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