Climate and monthly weather forecastAlton, IL
Climate and monthly weather forecast
Weather in January
January, like December, in Alton, Illinois, is another cold winter month, with temperature in the range of an average low of 23.2°F (-4.9°C) and an average high of 36.1°F (2.3°C). Alton's coldest weather arrives in January, when temperatures average a high of 36.1°F (2.3°C) and a low of 23.2°F (-4.9°C). Weather in January »Weather in February
The last month of the winter, February, is also a wintry month in Alton, Illinois, with an average temperature ranging between min 26.8°F (-2.9°C) and max 40.8°F (4.9°C). Alton registers an average high-temperature of a still icy 40.8°F (4.9°C) at the commencement of February, closely related to the preceding month. Weather in February »Weather in March
March, the first month of the spring in Alton, is a fresh month, with an average temperature varying between 37.2°F (2.9°C) and 53.2°F (11.8°C). March's arrival sees a rise in the average high-temperature, jumping from February's wintry 40.8°F (4.9°C) to a fresh 53.2°F (11.8°C). Weather in March »Weather in April
April is a refreshing spring month in Alton, Illinois, with temperature in the range of an average high of 64.6°F (18.1°C) and an average low of 46.8°F (8.2°C). Entering April, Alton sees a temperature rise, with the average high-temperature advancing from March's fresh 53.2°F (11.8°C) to a comfortable 64.6°F (18.1°C). Weather in April »Weather in May
The last month of the spring, May, is a moderately hot month in Alton, Illinois, with an average temperature ranging between min 56.8°F (13.8°C) and max 74.1°F (23.4°C). Alton's May weather shows an increase in high-temperatures, moving from April's enjoyable 64.6°F (18.1°C) to a warm 74.1°F (23.4°C). Weather in May »Weather in June
The first month of the summer, June, is still a warm month in Alton, Illinois, with an average temperature fluctuating between 82.9°F (28.3°C) and 65.8°F (18.8°C). Alton observes a slight uplift in the average high-temperature with the onset of June, adjusting from May's 74.1°F (23.4°C) to a still warm 82.9°F (28.3°C). Weather in June »Weather in July
July, like June, in Alton, Illinois, is a moderately hot summer month, with an average temperature fluctuating between 85.3°F (29.6°C) and 67.6°F (19.8°C). Alton's temperature records reveal July as the warmest month, marked by average highs of 85.3°F (29.6°C) and lows of 67.6°F (19.8°C). For July, the heat index is appraised at a fiery hot 96.8°F (36°C). Weather in July »Weather in August
August, the last month of the summer in Alton, is also a moderately hot month, with an average temperature varying between 84°F (28.9°C) and 65.7°F (18.7°C). August's commencement is accompanied by an average high-temperature of a still warm 84°F (28.9°C), diverging marginally from July's 85.3°F (29.6°C). Weather in August »Weather in September
September, the first month of the autumn in Alton, is also a moderately hot month, with an average temperature ranging between max 78.6°F (25.9°C) and min 59.5°F (15.3°C). The onset of September entails a subtle temperature shift, as the average high-temperature eases from a warm 84°F (28.9°C) in August to a still moderately hot 78.6°F (25.9°C). Weather in September »Weather in October
October, the same as September, is another comfortable autumn month in Alton, Illinois, with an average temperature fluctuating between 48.6°F (9.2°C) and 65.5°F (18.6°C). October comes with a decrease in the average high-temperature, falling from a moderately hot 78.6°F (25.9°C) in September to a comfortable 65.5°F (18.6°C). Weather in October »Weather in November
November, the last month of the autumn in Alton, is also a fresh month, with temperature in the range of an average low of 37°F (2.8°C) and an average high of 52.2°F (11.2°C). Arrival of November comes with a reduction in the average high-temperature, falling from an enjoyable 65.5°F (18.6°C) in October to a cool 52.2°F (11.2°C). Weather in November »Weather in December
The first month of the winter, December, is still a cold month in Alton, Illinois, with temperature in the range of an average high of 41.2°F (5.1°C) and an average low of 29.5°F (-1.4°C). With December's arrival, Alton's weather changes as the average high-temperature falls from a cool 52.2°F (11.2°C) in November to a wintry 41.2°F (5.1°C). Weather in December »Updated: Feb 12, 2024
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
January is Alton's coldest month, registering average high temperatures of 36.1°F (2.3°C) and lows of 23.2°F (-4.9°C).
In Alton, Illinois, during the entire year, the rain falls for 128.3 days and collects up to 18.9" (480mm) of precipitation.
January through March, November and December are months with snowfall.
Throughout the year, there are 17.9 snowfall days, and 3.58" (91mm) of snow is accumulated.
The months with the least sunshine are January and February, with an average of 4.5h of sunshine.
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2.
The month with the least rainfall is February, when the rain falls for 6 days and typically collects 0.83" (21mm) of precipitation.
The month with the most snowfall in Alton, Illinois, is February, when snow falls for 5.2 days and typically aggregates up to 1.14" (29mm) of snow.
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts in Alton, and the time zone changes from CST to CDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from CDT to CST.
In Alton, snow does not fall in April through October.
The month with the most rainfall in Alton is May, when the rain falls for 15.1 days and typically aggregates up to 2.44" (62mm) of precipitation.
June has the longest days of the year in Alton, with an average of 14h and 54min of daylight.
June has the most sunshine of the year, with an average of 10.4h of sunshine.
The months with the highest UV index in Alton are June through August, with an average maximum UV index of 6.
The average temperatures in Alton reach their apex in July, averaging 85.3°F (29.6°C) at the high end and 67.6°F (19.8°C) at the low end.
With an average relative humidity of 80%, July is the most humid month in Alton.
October is the least humid month, with an average relative humidity of 71%.
December has the shortest days of the year, with an average of 9h and 30min of daylight.
Average temperature
Alton, IL
The warmest month (with the highest average high temperature) is July (85.3°F).
The month with the lowest average high temperature is January (36.1°F).
The month with the highest average low temperature is July (67.6°F).
The coldest month (with the lowest average low temperature) is January (23.2°F).
Average pressure
Alton, IL
- Average pressure in January:
30.16"Hg - Average pressure in February:
30.12"Hg - Average pressure in March:
30.07"Hg - Average pressure in April:
29.94"Hg - Average pressure in May:
29.95"Hg - Average pressure in June:
29.92"Hg
- Average pressure in July:
29.97"Hg - Average pressure in August:
29.97"Hg - Average pressure in September:
30.02"Hg - Average pressure in October:
30.03"Hg - Average pressure in November:
30.12"Hg - Average pressure in December:
30.13"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed
Alton, IL
- Average wind speed in January:
9.6mph - Average wind speed in February:
9.5mph - Average wind speed in March:
9.3mph - Average wind speed in April:
9.3mph - Average wind speed in May:
7.5mph - Average wind speed in June:
6.6mph
- Average wind speed in July:
5.7mph - Average wind speed in August:
5.8mph - Average wind speed in September:
6.3mph - Average wind speed in October:
8.1mph - Average wind speed in November:
8.9mph - Average wind speed in December:
9mph
The windiest month (with the highest average wind speed) is January (9.6mph).
The calmest month (with the lowest average wind speed) is July (5.7mph).
Average humidity
Alton, IL
The month with the highest relative humidity is July (80%).
The month with the lowest relative humidity is October (71%).
Average rainfall
Alton, IL
- Average rainfall in January:
0.94" - Average rainfall in February:
0.83" - Average rainfall in March:
1.26" - Average rainfall in April:
2.01" - Average rainfall in May:
2.44" - Average rainfall in June:
2.17"
- Average rainfall in July:
2.05" - Average rainfall in August:
2.36" - Average rainfall in September:
1.3" - Average rainfall in October:
1.54" - Average rainfall in November:
1.06" - Average rainfall in December:
0.94"
The wettest month (with the highest rainfall) is May (2.44").
The driest month (with the least rainfall) is February (0.83").
Average rainfall days
Alton, IL
- Average rainfall days in January:
5.7 days - Average rainfall days in February:
6 days - Average rainfall days in March:
11.2 days - Average rainfall days in April:
13 days - Average rainfall days in May:
15.1 days - Average rainfall days in June:
13.9 days
- Average rainfall days in July:
15.4 days - Average rainfall days in August:
13.3 days - Average rainfall days in September:
10.5 days - Average rainfall days in October:
9.4 days - Average rainfall days in November:
8.5 days - Average rainfall days in December:
6.3 days
The month with the highest number of rainy days is July (15.4 days).
The month with the least rainy days is January (5.7 days).
Average snowfall
Alton, IL
The month with the highest snowfall is February (1.14").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days
Alton, IL
- Average snowfall days in January:
5.4 days - Average snowfall days in February:
5.2 days - Average snowfall days in March:
2.4 days - Average snowfall days in April:
0.3 days - Average snowfall days in May:
0 days - Average snowfall days in June:
0 days
- Average snowfall days in July:
0 days - Average snowfall days in August:
0 days - Average snowfall days in September:
0 days - Average snowfall days in October:
0.1 days - Average snowfall days in November:
0.9 days - Average snowfall days in December:
3.6 days
The month with the highest number of snowfall days is January (5.4 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight / Average sunshine
Alton, IL
- Average daylight in January:
9h and 48min - Average daylight in February:
10h and 48min - Average daylight in March:
12h and 0min - Average daylight in April:
13h and 12min - Average daylight in May:
14h and 18min - Average daylight in June:
14h and 54min
- Average daylight in July:
14h and 36min - Average daylight in August:
13h and 36min - Average daylight in September:
12h and 24min - Average daylight in October:
11h and 12min - Average daylight in November:
10h and 6min - Average daylight in December:
9h and 30min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in January:
4h and 30min - Average sunshine in February:
4h and 30min - Average sunshine in March:
6h and 18min - Average sunshine in April:
8h and 24min - Average sunshine in May:
9h and 18min - Average sunshine in June:
10h and 24min
- Average sunshine in July:
10h and 18min - Average sunshine in August:
10h and 6min - Average sunshine in September:
9h and 18min - Average sunshine in October:
6h and 6min - Average sunshine in November:
5h and 30min - Average sunshine in December:
4h and 54min
The month with the most sunshine is June (Average sunshine: 10h and 24min).
The months with the least sunshine are January and February (Average sunshine: 4h and 30min).
Average sunshine days
Alton, IL
- Average sunshine days in January:
20.9 days - Average sunshine days in February:
17 days - Average sunshine days in March:
16.1 days - Average sunshine days in April:
15.1 days - Average sunshine days in May:
13.7 days - Average sunshine days in June:
12.6 days
- Average sunshine days in July:
13.3 days - Average sunshine days in August:
15.3 days - Average sunshine days in September:
17.5 days - Average sunshine days in October:
20.6 days - Average sunshine days in November:
19.9 days - Average sunshine days in December:
21 days
The month with the most sunshine days is December (21 days).
The month with the least sunshine days is June (12.6 days).
Average UV index
Alton, IL
The months with the highest UV index are 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
Alton, IL
The month with the most cloud cover is January (Cloud cover 52).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility
Alton, IL
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).
