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
Transitioning into September, Walnut records an average high-temperature of a still hot 87.3°F (30.7°C), almost identical to August's 89.2°F (31.8°C). September presents a pronounced divergence from daily peak temperatures, with the average low-temperature of 64.4°F (18°C).Heat index
During September, the heat index is calculated to be a tropical 89.6°F (32°C). With constant exposure and activity, a state of weariness might ensue, leading to potential heat cramps.It is crucial to understand that heat index figures are for shade and gentle wind conditions. Direct exposure to sunshine could lead to a heat index increase by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'real feel', reflects the blend of air temperature and relative humidity to give a temperature impression. The influence of weather is personal, with a diverse population experiencing it differently due to differences in body mass, stature, and degree of activity. Exposure to direct sun rays can influence the heat you feel, pushing the heat index up by 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical to babies and toddlers. Young people are generally more susceptible than adults because they perspire less. Furthermore, their proportionally larger skin surface to their petite bodies and the increased heat output from their actions add to the risk.
Humidity
In Walnut, the average relative humidity in September is 48%.Rainfall
In Walnut, in September, it is raining for 2.1 days, with typically 0.08" (2mm) of accumulated precipitation. Throughout the year, there are 43.1 rainfall days, and 6.89" (175mm) of precipitation is accumulated.Daylight
In Walnut, the average length of the day in September is 12h and 22min.On the first day of September, 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 estimate of 6 to 7 represents a high health risk from exposure to the Sun's UV radiation for ordinary individuals.Note: The maximum daily UV index of 6 during September translates into the following directions:
Resist extreme sun exposure. Guarding against solar damage is essential. Try to minimize direct Sun exposure between 10 a.m. and 4 p.m., the peak period for UV radiation. Also note that objects like parasols or canopies might not provide complete sun protection. It's wise to wear UVA and UVB-blocking sunglasses when the sun shines brightly.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How hot is September?
What is the average humidity in September?
How many days does it rain in September?
How many hours of daylight does Walnut have in September?
When are sunrise and sunset in September?
How long on average sun shines in September?
What is the UV index intensity in September?
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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