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
The shift to September signals an average high-temperature of a still moderately hot 81.7°F (27.6°C), subtly varied from August's 82°F (27.8°C). September presents a pronounced divergence from daily peak temperatures in Napa Junction, with the average low-temperature of 56.3°F (13.5°C).Heat index
For September, the heat index is evaluated at 84.2°F (29°C). Constant exposure and activity lead to possible fatigue. Prolonged exercise may result in heat cramps.Heat index guidelines indicate values are for light wind scenarios and shaded regions. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'real feel', arises from combining readings of air temperature and relative moisture content. Factors such as metabolic variations, being pregnant, and physical activity can impact an individual's weather 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 highly critical to babies and toddlers. Youngsters are usually more at risk than adults, considering they sweat less. Additionally, their high skin surface area compared to their little bodies and their high heat production due to activity increases their risk.
Humidity
September is the least humid month, with an average relative humidity of 58%.Rainfall
In Napa Junction, during September, the rain falls for 2.5 days and regularly aggregates up to 0.08" (2mm) of precipitation. Throughout the year, in Napa Junction, California, there are 68.2 rainfall days, and 11.93" (303mm) of precipitation is accumulated.Daylight
In Napa Junction, 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 7:38 pm. On the last day of September, sunrise is at 7:04 am and sunset at 6:52 pm PDT.
Sunshine
The average sunshine in September in Napa Junction is 11.1h.UV index
The average daily maximum UV index in September is 5. A UV Index value of 3 to 5 symbolizes a moderate health risk from exposure to the Sun's UV rays for the average person.Note: A maximum high daily UV index of 5 during September translates into the following directions:
Exercise prevention - Warding off sunburn is urged. It's crucial to reduce time in the direct Sun around mid-day due to the intense solar radiation. Shield yourself from the harmful effects of UV radiation with sun-protective attire, a hat, and quality sunglasses.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in Napa Junction in September?
What is the least humid month in Napa Junction?
What is the average humidity in September in Napa Junction?
How many days does it rain in September in Napa Junction?
What is the average length of the day in September in Napa Junction?
When is the sunrise / sunset in September in Napa Junction?
How many hours of sunshine does Napa Junction have in September?
What is the UV index intensity in September in Napa Junction?
Average temperature in September
Napa Junction, CA
- Average high temperature in September: 81.7°F
The warmest month (with the highest average high temperature) is July (82.6°F).
The month with the lowest average high temperature is December (54.9°F).
- Average low temperature in September: 56.3°F
The month with the highest average low temperature is August (56.5°F).
The coldest months (with the lowest average low temperature) are January and December (42.3°F).
Average pressure in September
Napa Junction, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
Napa Junction, CA
- Average wind speed in September: 5.1mph
The windiest month (with the highest average wind speed) is May (6.6mph).
The calmest month (with the lowest average wind speed) is November (4.5mph).
Average humidity in September
Napa Junction, CA
- Average humidity in September: 58%
The month with the highest relative humidity is March (75%).
The month with the lowest relative humidity is September (58%).
Average rainfall in September
Napa Junction, CA
- Average rainfall in September: 0.08"
The wettest month (with the highest rainfall) is February (2.32").
The driest months (with the least rainfall) are July and August (0.04").
Average rainfall days in September
Napa Junction, CA
- Average rainfall days in September: 2.5 days
The month with the highest number of rainy days is March (11.9 days).
The month with the least rainy days is August (0.9 days).
Average daylight in September /
Average sunshine in September
Napa Junction, 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 36min).
- Average sunshine in September: 11h and 1min
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 42min).
Average sunshine days in September
Napa Junction, CA
- Average sunshine days in September: 26.8 days
The months with the most sunshine days are July and August (29.1 days).
The month with the least sunshine days is March (18.3 days).
Average UV index in September
Napa Junction, 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
Napa Junction, CA
- Average cloud cover in September: 10
The month with the most cloud cover is March (Cloud cover 37).
The month with the least cloud cover is July (Cloud cover 7).
Average visibility in September
Napa Junction, 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).
Napa Junction, California, USA
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