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 snowfall in September
- Average snowfall 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
September
Weather in September
Temperature
During the shift to September, O'Brien records a mild decrease in average high-temperature, moving from a hot 90.1°F (32.3°C) in August to a moderately hot 84°F (28.9°C). A stark contrast in day to night temperatures can be seen in September, with an average low-temperature of 54.3°F (12.4°C).Heat index
During September, the heat index is appraised at 84.2°F (29°C). If exposure and activity persist, fatigue could ensue, possibly leading to heat cramps.One should consider that heat index numbers are for shaded settings and light wind. When under direct sunshine, the heat index may be elevated by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'felt air temperature', determines the feeling of heat when you account for the relative humidity. Additional elements including metabolic differences, the level of physical activity, and attire have a role in shaping the individual's temperature perception. It is noteworthy to mention that direct sunlight exposure can augment the felt temperature, leading to an increase in the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for babies and toddlers. Children are often less aware of the need to rest and re-hydrate. Thirst is a late sign of dehydration - it's vital to remain hydrated, particularly during prolonged physical activities.
Humidity
The average relative humidity in September is 40%.Rainfall
In O'Brien, in September, it is raining for 3.4 days, with typically 0.31" (8mm) of accumulated precipitation. Throughout the year, there are 102.3 rainfall days, and 24.21" (615mm) of precipitation is accumulated.Snowfall
In O'Brien, snow does not fall in April through October.Daylight
The average length of the day in September is 12h and 27min.On the first day of September, sunrise is at 6:37 am and sunset at 7:41 pm. On the last day of the month, sunrise is at 7:05 am and sunset at 6:52 pm PDT.
Sunshine
In September, the average sunshine is 11h.UV index
In O'Brien, 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: In September, the average maximum UV index of 5 translates into the following recommendations:
Stay alert. Light-skinned people could suffer burns in less than 30 minutes. Direct exposure to the Sun during its peak hours around mid-day should be minimized for safety. 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
How hot does it get in September?
What is the average humidity in September?
How many days does it rain in September?
When it does not snow in O'Brien?
How many hours of daylight does O'Brien have in September?
When are sunrise and sunset in September?
How many hours of sunshine does O'Brien have in September?
What is the UV index reading in September?
Average temperature in September
O'Brien, CA
- Average high temperature in September: 84°F
The warmest month (with the highest average high temperature) is July (91.6°F).
The month with the lowest average high temperature is December (47.8°F).
- Average low temperature in September: 54.3°F
The month with the highest average low temperature is July (59.4°F).
The coldest month (with the lowest average low temperature) is December (33.6°F).
Average pressure in September
O'Brien, CA
- Average pressure in September: 29.95"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is August (29.92"Hg).
Average wind speed in September
O'Brien, CA
- Average wind speed in September: 5mph
The windiest months (with the highest average wind speed) are March and October (5.3mph).
The calmest months (with the lowest average wind speed) are August and November (4.5mph).
Average humidity in September
O'Brien, CA
- Average humidity in September: 40%
The month with the highest relative humidity is March (77%).
The month with the lowest relative humidity is August (37%).
Average rainfall in September
O'Brien, CA
- Average rainfall in September: 0.31"
The wettest month (with the highest rainfall) is March (4.8").
The driest month (with the least rainfall) is July (0.12").
Average rainfall days in September
O'Brien, CA
- Average rainfall days in September: 3.4 days
The month with the highest number of rainy days is March (16.8 days).
The month with the least rainy days is August (1.7 days).
Average snowfall in September
O'Brien, CA
- Average snowfall in September: 0"
The month with the highest snowfall is November (1.3").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in September
O'Brien, CA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (1.9 days).
The months with the least snowfall days are April, May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
O'Brien, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 11h and 0min
The month with the most sunshine is July (Average sunshine: 12h and 12min).
The month with the least sunshine is December (Average sunshine: 5h and 18min).
Average sunshine days in September
O'Brien, CA
- Average sunshine days in September: 25.2 days
The month with the most sunshine days is August (27.1 days).
The month with the least sunshine days is March (11.8 days).
Average UV index in September
O'Brien, CA
- Average UV index in September: 5
The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are February, November and December (UV index 2).
Average cloud cover in September
O'Brien, CA
- Average cloud cover in September: 9
The month with the most cloud cover is March (Cloud cover 44).
The month with the least cloud cover is August (Cloud cover 5).
Average visibility in September
O'Brien, CA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October and November (6mi).
The month with the lowest visibility is December (5mi).