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 signifies a gentle decline in Alton's average high-temperature, easing from 85.6°F (29.8°C) in August to a still warm 79.3°F (26.3°C). During the month of September, the nighttime temperature falls to an average of 59.9°F (15.5°C).Humidity
The average relative humidity in September in Alton is 75%.Rainfall
September is the month with the least rainfall. Rain falls for 12.5 days and accumulates 1.61" (41mm) of precipitation.Snowfall
January through April, September through December are months with snowfall in Alton. September is the first month it typically snows in Alton. Throughout September, in the average 0.1 snowfall days, it receives 0.04" (1mm) of snow. In Alton, during the entire year, snow falls for 26.8 days and aggregates up to 7.91" (201mm) of snow.Daylight
The average length of the day in September is 12h and 25min.On the first day of the month, sunrise is at 7:16 am and sunset at 8:14 pm. On the last day of September, sunrise is at 7:41 am and sunset at 7:29 pm EDT.
Sunshine
The average sunshine in September in Alton is 8.4h.UV index
In September, the average daily maximum UV index in Alton is 5. A UV Index estimate of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV rays for average individuals.Note: A maximum UV index of 5 in September translates into the following recommendations:
Take necessary precautions - Protection from skin and eye injury is mandatory. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. Using UVA and UVB-protective sunglasses and sun-protective clothing is effective against UV radiation. Beware! The strength of the UV rays is increased nearly double-fold by the reflection of the snow.
Frequently asked questions
What are September temperatures in Alton?
What is the average humidity in September in Alton?
What is the driest month in Alton?
How many days does it rain in September in Alton?
When does it start to snow in Alton?
What is the average length of the day in September in Alton?
What time are sunrise and sunset in September in Alton?
How many hours of sunshine does Alton have in September?
What is the UV index reading in September in Alton?
Average temperature in September
Alton, IN
- Average high temperature in September: 79.3°F
The warmest month (with the highest average high temperature) is July (86.5°F).
The month with the lowest average high temperature is January (38.8°F).
- Average low temperature in September: 59.9°F
The month with the highest average low temperature is July (67.1°F).
The coldest month (with the lowest average low temperature) is January (25.7°F).
Average pressure in September
Alton, IN
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.95"Hg).
Average wind speed in September
Alton, IN
- Average wind speed in September: 5.3mph
The windiest months (with the highest average wind speed) are January and February (7.7mph).
The calmest months (with the lowest average wind speed) are July and August (4.8mph).
Average humidity in September
Alton, IN
- Average humidity in September: 75%
The months with the highest relative humidity are February and December (80%).
The month with the lowest relative humidity is October (74%).
Average rainfall in September
Alton, IN
- Average rainfall in September: 1.61"
The wettest month (with the highest rainfall) is April (3.31").
The driest month (with the least rainfall) is September (1.61").
Average rainfall days in September
Alton, IN
- Average rainfall days in September: 12.5 days
The month with the highest number of rainy days is May (18.7 days).
The month with the least rainy days is November (9.8 days).
Average snowfall in September
Alton, IN
- Average snowfall in September: 0.04"
The month with the highest snowfall is January (2.24").
The months with the least snowfall are May, June, July and August (0").
Average snowfall days in September
Alton, IN
- Average snowfall days in September: 0.1 days
The month with the highest number of snowfall days is January (7.6 days).
The months with the least snowfall days are May, June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Alton, IN
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in September: 8h and 2min
The month with the most sunshine is July (Average sunshine: 10h and 18min).
The month with the least sunshine is December (Average sunshine: 4h and 24min).
Average sunshine days in September
Alton, IN
- Average sunshine days in September: 14.8 days
The month with the most sunshine days is October (19.1 days).
The month with the least sunshine days is May (11.1 days).
Average UV index in September
Alton, IN
- Average UV index in September: 5
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Alton, IN
- Average cloud cover in September: 32
The month with the most cloud cover is January (Cloud cover 56).
The month with the least cloud cover is August (Cloud cover 29).
Average visibility in September
Alton, IN
- Average visibility in September: 5mi
The months with the highest visibility are March, April, June, August, October and November (6mi).
The months with the lowest visibility are January, February, May, July, September and December (5mi).
Alton, Indiana, USA
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