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
Altadena's average high-temperature marks a warm 84.6°F (29.2°C) with the advent of September, closely mirroring that of the preceding month. Altadena observes a distinct decrease from peak daytime temperatures, with an average low-temperature of 62.6°F (17°C) throughout the month of September.Heat index
September's mean heat index is estimated at a tropical 86°F (30°C). Exposure and extended activity could potentially cause a state of fatigue and lead to heat cramps.Know that the heat index computations account for shaded terrains and slight winds. Exposure to direct sunlight may make the heat index values climb by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature' or 'feels like', combines both the air temperature and the humidity level to give a perceived human temperature. An individual's perception of weather can be influenced by a variety of factors including metabolic differences, being pregnant, and their degree of physical exertion. When in direct sunlight, one should be cautious as it can raise the heat index by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are extremely significant for children. Children often miss understanding the importance of rest and rehydration. Thirst usually appears late during dehydration - therefore, maintaining hydration, particularly during long physical activities, is essential.
Humidity
The average relative humidity in September in Altadena is 49%.Rainfall
In September, the rain falls for 3 days. Throughout September, 0.16" (4mm) of precipitation is accumulated. Throughout the year, in Altadena, there are 52 rainfall days, and 8.82" (224mm) of precipitation is accumulated.Daylight
In September, the average length of the day in Altadena is 12h and 22min.On the first day of September, sunrise is at 6:26 am and sunset at 7:17 pm. On the last day of the month, sunrise is at 6:46 am and sunset at 6:37 pm PDT.
Sunshine
The average sunshine in September in Altadena is 10.8h.UV index
June through September, with an average maximum UV index of 6, are months with the highest UV index in Altadena. A UV Index value of 6 to 7 symbolizes a high health vulnerability from exposure to the Sun's UV rays for ordinary individuals.Note: A daily high UV index of 6 in September leads to these guidelines:
Fend off overexposure. Sun protection is vital. It's important to stay in the shade and limit exposure to the sun from 10 a.m. to 4 p.m., when UV radiation is most intense, although remember that shade structures may not provide full sun protection. A hat with a broad brim is indispensable, filtering out up to half of UV rays.
Frequently asked questions
How hot does it get in Altadena in September?
What is the average humidity in September in Altadena?
How many days does it rain in September in Altadena?
How many hours of daylight does Altadena have in September?
When is the sunrise / sunset in September in Altadena?
How long on average sun shines in September in Altadena?
What is the month with the highest UV index in Altadena?
What is the UV index reading in September in Altadena?
Average temperature in September
Altadena, CA
- Average high temperature in September: 84.6°F
The warmest month (with the highest average high temperature) is August (86.2°F).
The month with the lowest average high temperature is December (61°F).
- Average low temperature in September: 62.6°F
The month with the highest average low temperature is August (64.4°F).
The coldest month (with the lowest average low temperature) is December (45.5°F).
Average pressure in September
Altadena, CA
- Average pressure in September: 29.89"Hg
The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).
Average wind speed in September
Altadena, CA
- Average wind speed in September: 4.4mph
The windiest month (with the highest average wind speed) is April (5.8mph).
The calmest month (with the lowest average wind speed) is September (4.4mph).
Average humidity in September
Altadena, CA
- Average humidity in September: 49%
The months with the highest relative humidity are March, May and June (56%).
The month with the lowest relative humidity is November (46%).
Average rainfall in September
Altadena, CA
- Average rainfall in September: 0.16"
The wettest month (with the highest rainfall) is February (1.81").
The driest month (with the least rainfall) is June (0.04").
Average rainfall days in September
Altadena, CA
- Average rainfall days in September: 3 days
The month with the highest number of rainy days is March (7.5 days).
The month with the least rainy days is June (1.3 days).
Average daylight in September /
Average sunshine in September
Altadena, 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 months with the most sunshine are June and July (Average sunshine: 12h and 6min).
The months with the least sunshine are February and December (Average sunshine: 6h and 54min).
Average sunshine days in September
Altadena, CA
- Average sunshine days in September: 25.6 days
The month with the most sunshine days is June (27.2 days).
The month with the least sunshine days is February (21.3 days).
Average UV index in September
Altadena, CA
- Average UV index in September: 6
The months with the highest UV index are June, July, August and September (UV index 6).
The month with the lowest UV index is December (UV index 3).
Average cloud cover in September
Altadena, CA
- Average cloud cover in September: 6
The month with the most cloud cover is March (Cloud cover 22).
The month with the least cloud cover is August (Cloud cover 5).
Average visibility in September
Altadena, 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).
Altadena, California, USA
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