Alton (IL) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Alton.
Climate overview of Alton
Alton, Illinois, United States of America, sees big temperature differences between seasons, with July peaking at 31°C (88°F) and January dropping to 4°C (39°F).
Rain/snowfall is high, totalling around 1007 mm (40 in) per year. April is the wettest month and January the driest. July is the sunniest month, averaging 10.4 hours of sunshine per day.
Alton Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Alton — and find the best time to visit.
Monthly Temperature in Alton
Visitors to Alton can expect significant temperature changes throughout the year. Average maximum daytime temperatures range from a very warm 31°C (88°F) in July, the warmest time of the year, to a chilly 4°C (39°F) during cooler months like January.
At night, you can expect temperatures ranging from 21°C (70°F) in July to around -5°C (23°F) during January.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Alton
Alton is known for its substantial rain/snowfall, with annual precipitation reaching 1007 mm (40 in). Significant seasonal changes in precipitation occur throughout the year. In the wettest month, April it receives high rainfall, averaging 115 mm (4.5 in) of precipitation, recorded across 11 rainy days. In contrast, the driest month January brings less snow/rainfall, with 42 mm (1.7 in) over 7 snowy/rainy days. For more details, please visit our Alton Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Sunshine Hours in Alton
Seasonal changes in sunshine hours are quite dramatic in Alton. While July receives considerable daily sunshine with up to 10.4 hours, December marks the darkest time of the year, where sunshine is scarce with only 4.3 hours of sunlight per day.
Visit our detailed sunshine hours page for more information.
Monthly hours of sunshine
Daily hours of sunshine
Daily percentage of sunshine
Humidity in Alton by Month
The relative humidity is high throughout the year in Alton.
The city experiences its highest humidity in December, reaching 74%. In April, the humidity drops to its lowest level at 63%. What does this mean? Read our detailed page on humidity levels for further details.
Relative humidity over the year
Best Time to Visit Alton
The weather does bring rainfall during this period, between 79 mm (3.1 in) and 115 mm (4.5 in). Seeking the perfect travel destination for this year? We've created a tool that suggests locations matching your desired weather. Let our weather planner guide your travel decisions.
Frequently asked questions about the climate in Alton
What is the best time to visit Alton?
September and October typically offer the most optimal weather in Alton. In contrast, January, February and December tend to have less optimal conditions.
What temperatures can I expect in Alton?
Daytime highs range from 4°C (39°F) in January to 31°C (88°F) in July. Nighttime lows range from -5°C (23°F) to 21°C (70°F). Temperatures vary considerably through the year.
How much rain does Alton get?
Annual rainfall is around 1007 mm (40 in). April is the wettest month with 115 mm (4.5 in), while January is the driest with 42 mm (1.7 in).
How sunny is Alton?
Alton receives around 2,594 hours of sunshine per year. July is the sunniest month with 311 hours, while December is the cloudiest with just 128 hours. Overall, Alton enjoys abundant sunshine.
Alton 3-Day Forecast
Alton (IL) 3-Day Forecast
Alton on the map
Alton is highlighted — select any city to see its climate.
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