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's weather records an average high-temperature of a still moderately hot 79°F (26.1°C), showing little deviation from August. In Graton, the nighttime temperature registers a significant drop from daytime peaks to an average of 54.7°F (12.6°C) in September.Humidity
September is the least humid month, with an average relative humidity of 63%.Rainfall
In Graton, during September, the rain falls for 2.8 days and regularly aggregates up to 0.12" (3mm) of precipitation. Throughout the year, there are 72.8 rainfall days, and 12.01" (305mm) of precipitation is accumulated.Daylight
The average length of the day in September in Graton is 12h and 25min.On the first day of the month, sunrise is at 6:41 am and sunset at 7:40 pm. On the last day of September, in Graton, sunrise is at 7:07 am and sunset at 6:55 pm PDT.
Sunshine
In Graton, the average sunshine in September is 11h.UV index
In Graton, California, the average daily maximum UV index in September is 5. A UV Index estimate of 3 to 5 represents a moderate threat to health from unprotected exposure to Sun's UV rays for the average person.Note: The daily high UV index of 5 in September translates into this advice:
Be vigilant - Preventing sunburn is recommended. UV radiation from the Sun is most dangerous during midday; take precautions and seek shade. A wide-brimmed hat is a shield, deflecting up to 50% of harmful UV radiation from eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the least humid month?
What is the average humidity in September?
How many days does it rain in September?
What is the average length of the day in September?
What time are sunrise and sunset in September?
How long on average sun shines in September?
What is the UV index reading in September?
Average temperature in September
Graton, CA
- Average high temperature in September: 79°F
The warmest month (with the highest average high temperature) is August (79.7°F).
The month with the lowest average high temperature is December (55.6°F).
- Average low temperature in September: 54.7°F
The months with the highest average low temperature are August and September (54.7°F).
The coldest month (with the lowest average low temperature) is December (41.9°F).
Average pressure in September
Graton, 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
Graton, CA
- Average wind speed in September: 5.2mph
The windiest month (with the highest average wind speed) is May (7.1mph).
The calmest month (with the lowest average wind speed) is November (4.9mph).
Average humidity in September
Graton, CA
- Average humidity in September: 63%
The month with the highest relative humidity is March (77%).
The month with the lowest relative humidity is September (63%).
Average rainfall in September
Graton, CA
- Average rainfall in September: 0.12"
The wettest month (with the highest rainfall) is February (2.64").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in September
Graton, CA
- Average rainfall days in September: 2.8 days
The month with the highest number of rainy days is March (12.6 days).
The month with the least rainy days is August (0.8 days).
Average daylight in September /
Average sunshine in September
Graton, CA
- Average daylight in September: 12h and 2min
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 30min).
- Average sunshine in September: 11h and 0min
The month with the most sunshine is July (Average sunshine: 11h and 54min).
The month with the least sunshine is December (Average sunshine: 5h and 42min).
Average sunshine days in September
Graton, CA
- Average sunshine days in September: 26.5 days
The month with the most sunshine days is July (27.2 days).
The month with the least sunshine days is March (17.1 days).
Average UV index in September
Graton, 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 January, February, November and December (UV index 3).
Average cloud cover in September
Graton, CA
- Average cloud cover in September: 10
The month with the most cloud cover is March (Cloud cover 39).
The month with the least cloud cover is July (Cloud cover 9).
Average visibility in September
Graton, 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).
Graton, California, USA
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