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 average high-temperature in September, at a moderately hot 85.5°F (29.7°C), reveals a modest deviation from August's 88.2°F (31.2°C). In September, the temperature sees a substantial plunge from daytime highs to a low average of 62.8°F (17.1°C).Heat index
In September, the heat index is estimated at a tropical 86°F (30°C). When exposure and activity are sustained, they could induce fatigue, with a chance of heat cramps.Heat index guidelines indicate values are for light wind scenarios and shaded regions. The presence of direct sunlight can raise the heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel' or 'feels like', is a measure that combines air temperature and relative humidity into a single value that indicates how hot the weather feels. Factors including metabolic differences, physical activity, and clothing are additional elements that influence the individual's temperature experience. In the direct sunlight, the weather's impact can be amplified, possibly boosting the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical to babies and toddlers. 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
In September, the average relative humidity is 48%.Rainfall
In September, the rain falls for 2.6 days. Throughout September, 0.12" (3mm) of precipitation is accumulated. In Monrovia, during the entire year, the rain falls for 50.9 days and collects up to 8.46" (215mm) of precipitation.Daylight
The average length of the day in September is 12h and 22min.On the first day of the month, sunrise is at 6:26 am and sunset at 7:17 pm. On the last day of September, in Monrovia, sunrise is at 6:46 am and sunset at 6:37 pm PDT.
Sunshine
The average sunshine in September is 10.8h.UV index
The months with the highest UV index are June through September, with an average maximum UV index of 6. A UV Index value of 6 to 7 symbolizes a high health risk from unprotected exposure to Sun's UV rays for ordinary individuals.Note: A daily maximum UV index of 6 in September translates into the following instructions:
Uphold preventive measures and conform to sun safety guidelines. Defending against skin and eye harm is crucial. Stay in the shade and limit direct sun exposure between 10 a.m. and 4 p.m., when UV radiation is at its strongest. Remember, however, that not all shade structures provide full sun protection. For a sun-safe wardrobe, go for clothes that are tightly woven and generously sized.
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 much does it rain in September?
What is the average length of the day in September in Monrovia?
When are sunrise and sunset in September?
How long on average sun shines in September?
What are the months with the highest UV index?
What is the UV index reading in September?
Average temperature in September
Monrovia, CA
- Average high temperature in September: 85.5°F
The warmest month (with the highest average high temperature) is August (88.2°F).
The month with the lowest average high temperature is December (61.7°F).
- Average low temperature in September: 62.8°F
The month with the highest average low temperature is August (64.8°F).
The coldest month (with the lowest average low temperature) is December (45.7°F).
Average pressure in September
Monrovia, 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
Monrovia, CA
- Average wind speed in September: 4.5mph
The windiest month (with the highest average wind speed) is April (5.8mph).
The calmest month (with the lowest average wind speed) is September (4.5mph).
Average humidity in September
Monrovia, CA
- Average humidity in September: 48%
The months with the highest relative humidity are March and May (56%).
The month with the lowest relative humidity is November (46%).
Average rainfall in September
Monrovia, CA
- Average rainfall in September: 0.12"
The wettest months (with the highest rainfall) are February and December (1.77").
The driest month (with the least rainfall) is June (0.04").
Average rainfall days in September
Monrovia, CA
- Average rainfall days in September: 2.6 days
The month with the highest number of rainy days is March (7.4 days).
The month with the least rainy days is June (1.1 days).
Average daylight in September /
Average sunshine in September
Monrovia, 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 months with the least sunshine are January, February and December (Average sunshine: 6h and 54min).
Average sunshine days in September
Monrovia, CA
- Average sunshine days in September: 26.2 days
The month with the most sunshine days is June (28.3 days).
The month with the least sunshine days is February (21 days).
Average UV index in September
Monrovia, 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
Monrovia, CA
- Average cloud cover in September: 7
The months with the most cloud cover are March and December (Cloud cover 22).
The month with the least cloud cover is August (Cloud cover 5).
Average visibility in September
Monrovia, 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).
Monrovia, California, USA
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