September weather forecastAlton, IN
September
Weather in September
September, the first month of the autumn in Alton, is still a warm month, with temperature in the range of an average low of 59.9°F (15.5°C) and an average high of 79.3°F (26.3°C).Temperature
The start of September signals a gentle decrease in the average high-temperature, transitioning from a warm 85.6°F (29.8°C) in August to a still moderately hot 79.3°F (26.3°C). In Alton, September nights witness a steady temperature drop to a refreshing 59.9°F (15.5°C).Humidity
In Alton, the average relative humidity in September is 75%.Rainfall
The month with the least rainfall in Alton is September, when the rain falls for 12.5 days and typically collects 1.61" (41mm) of precipitation.Snowfall
Months with snowfall are January through April, September through December. September is the first month it typically snows. 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
In Alton, the average length of the day in September is 12h and 25min.On the first day of September, sunrise is at 7:16 am and sunset at 8:14 pm. On the last day of the month, sunrise is at 7:41 am and sunset at 7:29 pm EDT.
Sunshine
The average sunshine in September is 8.4h.UV index
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 the average person.Note: The maximum UV index of 5 during September translates into these guidelines:
Take precautions. Light skin individuals may get burned in less than 30 minutes. To prevent harmful UV exposure, minimize direct contact with the Sun around midday. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes. Mind you! Snow reflection can increase the intensity of the Sun's UV radiation nearly twofold.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
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 24min
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 24min
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).
