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 snowfall in September
- Average snowfall 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
September witnesses a gentle descent in average high-temperature, descending from August's tropical 88.3°F (31.3°C) to a moderately hot 81.9°F (27.7°C). During September nights, Alton witnesses a consistent average temperature of 60.8°F (16°C).Heat index
During September, the heat index is computed to be a hot 86°F (30°C). Exhaustion becomes probable with enduring exposure and activity, potentially causing heat cramps.Given the heat index, its values are aligned with shaded sites and gentle winds. Heat index values can rise by 15 Fahrenheit (8 Celsius) degrees when in direct sunlight.
Note: The heat index, also known as 'real feel' or 'felt air temperature', is an estimation of the warmth sensation when considering humidity levels. Metabolic differences, pregnancy status, and the level of physical activity are additional factors influencing an individual's weather perception. Remember, direct sunlight exposure can heighten the heat impact and might increase the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are extremely significant for children. 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
In September, the average relative humidity is 73%.Rainfall
The month with the least rainfall is September, when the rain falls for 12 days and typically collects 1.57" (40mm) of precipitation.Snowfall
May through October are months without snowfall.Daylight
In Alton, the average length of the day in September is 12h and 24min.On the first day of September, sunrise is at 6:37 am and sunset at 7:33 pm. On the last day of the month, sunrise is at 7:00 am and sunset at 6:50 pm CDT.
Sunshine
In September, the average sunshine is 9.4h.UV index
In Alton, the average daily maximum UV index in September is 5. A UV Index reading of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for average individuals.Note: An average maximum UV index of 5 in September leads to these recommendations:
Exercise care. People with light skin might get burns in fewer than 30 minutes. Midday is when the Sun's radiation is strongest; avoid prolonged exposure during this time. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the average humidity in September?
What is the driest month in Alton?
How much does it rain in September?
When it does not snow?
How many hours of daylight does Alton have in September?
What time are sunrise and sunset in September?
How long on average sun shines in September?
How high is the UV index in September?
Average temperature in September
Alton, MO
- Average high temperature in September: 81.9°F
The warmest month (with the highest average high temperature) is July (89.4°F).
The month with the lowest average high temperature is January (43.3°F).
- Average low temperature in September: 60.8°F
The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (28.4°F).
Average pressure in September
Alton, MO
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
Alton, MO
- Average wind speed in September: 5.7mph
The windiest months (with the highest average wind speed) are January, February, March and April (8.1mph).
The calmest months (with the lowest average wind speed) are July and August (5.3mph).
Average humidity in September
Alton, MO
- Average humidity in September: 73%
The months with the highest relative humidity are March and May (79%).
The month with the lowest relative humidity is October (72%).
Average rainfall in September
Alton, MO
- Average rainfall in September: 1.57"
The wettest month (with the highest rainfall) is May (4.25").
The driest month (with the least rainfall) is September (1.57").
Average rainfall days in September
Alton, MO
- Average rainfall days in September: 12 days
The month with the highest number of rainy days is May (16.5 days).
The month with the least rainy days is January (8.6 days).
Average snowfall in September
Alton, MO
- Average snowfall in September: 0"
The month with the highest snowfall is February (1.26").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in September
Alton, MO
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (2.8 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Alton, MO
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 36min).
The month with the shortest days is December (Average daylight: 9h and 42min).
- Average sunshine in September: 9h and 2min
The month with the most sunshine is June (Average sunshine: 10h and 24min).
The month with the least sunshine is February (Average sunshine: 4h and 48min).
Average sunshine days in September
Alton, MO
- Average sunshine days in September: 16.5 days
The month with the most sunshine days is December (19.6 days).
The month with the least sunshine days is May (12.3 days).
Average UV index in September
Alton, MO
- Average UV index in September: 5
The month with the highest UV index is June (UV index 7).
The months with the lowest UV index are January and December (UV index 2).
Average cloud cover in September
Alton, MO
- Average cloud cover in September: 31
The month with the most cloud cover is March (Cloud cover 49).
The month with the least cloud cover is June (Cloud cover 29).
Average visibility in September
Alton, MO
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, June, August, September, October, November and December (6mi).
The months with the lowest visibility are May and July (5mi).
Alton, Missouri, USA
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