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 tropical 87.3°F (30.7°C), subtly varied from August's 89.2°F (31.8°C). Nighttime in September brings a stark departure from the daily high, resting at an average low-temperature of 64.4°F (18°C).Heat index
September's heat index is computed to be a hot 89.6°F (32°C). If one sustains activity during exposure, it could lead to a sense of fatigue, with a chance of heat cramps.Be informed that the heat index values are oriented around shady conditions and gentle breezes. Direct sunshine exposure could raise heat index values by as much as 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel' or 'felt air temperature', is an index that combines air temperature and relative humidity to determine the human-perceived temperature equivalent. One's perception of weather can be shaped by other factors, involving metabolic differences, pregnancy, and physical exertion. When exposed to direct sunlight, it's possible for the heat index to increase by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are primarily vital for children. Children usually face more risks than adults as their ability to sweat is less. Additionally, their larger skin surface in relation to their petite bodies and higher heat output due to their activities increases their vulnerability.
Humidity
The average relative humidity in September is 48%.Rainfall
In Walnut, during September, the rain falls for 2.1 days and regularly aggregates up to 0.08" (2mm) of precipitation. In Walnut, California, during the entire year, the rain falls for 43.1 days and collects up to 6.89" (175mm) of precipitation.Daylight
In Walnut, the average length of the day in September is 12h and 22min.On the first day of September in Walnut, California, sunrise is at 6:25 am and sunset at 7:16 pm. On the last day of the month, sunrise is at 6:45 am and sunset at 6:36 pm PDT.
Sunshine
In Walnut, the average sunshine in September is 10.8h.UV index
In Walnut, the average daily maximum UV index in September is 6. A UV Index value of 6 to 7 symbolizes a high health vulnerability from unsafe exposure to UV radiation for average individuals.Note: The UV index of 6 during September leads to these advisories:
Deter overexposure. Protecting against the sun's effects is essential. The Sun emits the most powerful UV radiation between 10 a.m. and 4 p.m. Try to avoid direct sunlight during this period. For holistic sun protection encompassing the eyes, ears, face, and neck, a wide-brim hat is key.
Frequently asked questions
Is it hot in Walnut during September?
What is the average humidity in September in Walnut?
How much does it rain in Walnut in September?
How many hours of daylight does Walnut have in September?
What time are sunrise and sunset in September in Walnut?
How many hours of sunshine does Walnut have in September?
What is the UV index reading in September in Walnut?
Average temperature in September
Walnut, CA
- Average high temperature in September: 87.3°F
The warmest month (with the highest average high temperature) is August (89.2°F).
The month with the lowest average high temperature is December (63.7°F).
- Average low temperature in September: 64.4°F
The month with the highest average low temperature is August (66.2°F).
The coldest months (with the lowest average low temperature) are February and December (47.7°F).
Average pressure in September
Walnut, CA
- Average pressure in September: 29.88"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is June (29.87"Hg).
Average wind speed in September
Walnut, CA
- Average wind speed in September: 4.5mph
The windiest months (with the highest average wind speed) are April and May (5.7mph).
The calmest month (with the lowest average wind speed) is September (4.5mph).
Average humidity in September
Walnut, CA
- Average humidity in September: 48%
The months with the highest relative humidity are May and June (56%).
The month with the lowest relative humidity is November (45%).
Average rainfall in September
Walnut, CA
- Average rainfall in September: 0.08"
The wettest month (with the highest rainfall) is December (1.57").
The driest months (with the least rainfall) are June and August (0.04").
Average rainfall days in September
Walnut, CA
- Average rainfall days in September: 2.1 days
The month with the highest number of rainy days is March (6.6 days).
The month with the least rainy days is June (1 days).
Average daylight in September /
Average sunshine in September
Walnut, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 9h and 54min).
- Average sunshine in September: 10h and 5min
The month with the most sunshine is July (Average sunshine: 12h and 6min).
The month with the least sunshine is February (Average sunshine: 6h and 48min).
Average sunshine days in September
Walnut, CA
- Average sunshine days in September: 26.7 days
The month with the most sunshine days is June (28.6 days).
The month with the least sunshine days is February (22 days).
Average UV index in September
Walnut, CA
- Average UV index in September: 6
The months with the highest UV index are July and August (UV index 7).
The months with the lowest UV index are January, February, November and December (UV index 4).
Average cloud cover in September
Walnut, CA
- Average cloud cover in September: 7
The months with the most cloud cover are February, March and December (Cloud cover 21).
The month with the least cloud cover is August (Cloud cover 5).
Average visibility in September
Walnut, 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).
Walnut, California, USA
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