Decatur (IL) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Decatur.
Climate overview of Decatur
Decatur, Illinois, United States of America, experiences significant temperature variation throughout the year. Summers bring daytime highs of 30°C (86°F) in July, while winters cool to 2°C (36°F) in January.
Rain/snowfall is high, totalling around 1057 mm (42 in) per year. June is the wettest month and January the driest. The most sunshine falls in July, with an average of 10.7 hours of daily sunshine.
Decatur Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Decatur — and find the best time to visit.
Monthly Temperature in Decatur
Depending on the time of the year, temperatures range from comfortable to chilly in Decatur. Average maximum daytime temperatures range from a comfortable 30°C (86°F) in July, the warmest time of the year, to a chilly 2°C (36°F) during cooler months like January.
At night, you can expect temperatures ranging from 19°C (66°F) in July to around -7°C (19°F) during January.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Decatur
Decatur has a relatively rain/snowy climate with high precipitation levels, averaging 1057 mm (42 in) of rain/snowfall annually. Significant seasonal changes in precipitation occur throughout the year. In the wettest month, June it receives high rainfall, averaging 149 mm (5.9 in) of precipitation, recorded across 12 rainy days. In contrast, the driest month January brings less snow/rainfall, with 43 mm (1.7 in) over 8 snowy/rainy days. For more details, please visit our Decatur 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 Decatur
Seasonal changes in sunshine hours are quite dramatic in Decatur. While July receives considerable daily sunshine with up to 10.7 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 Decatur by Month
The relative humidity is high throughout the year in Decatur.
The city experiences its highest humidity in December, reaching 78%. In April, the humidity drops to its lowest level at 65%. What does this mean? Read our detailed page on humidity levels for further details.
Relative humidity over the year
Best Time to Visit Decatur
Rainfall during this time ranges from 65 mm (2.6 in) in August to 149 mm (5.9 in) in June. This means you can expect a mix of sunny days and occasional showers. Need help choosing your next travel destination? We offer a specialized tool that matches you with locations based on your weather preferences. Explore destinations that suit your climate preferences.
Frequently asked questions about the climate in Decatur
What is the best time to visit Decatur?
August and September typically offer the most optimal weather in Decatur. In contrast, January, February and December tend to have less optimal conditions.
What temperatures can I expect in Decatur?
Daytime highs range from 2°C (36°F) in January to 30°C (86°F) in July. Nighttime lows range from -7°C (19°F) to 19°C (66°F). Temperatures vary considerably through the year.
How much rain does Decatur get?
Annual rainfall is around 1057 mm (42 in). June is the wettest month with 149 mm (5.9 in), while January is the driest with 43 mm (1.7 in).
How sunny is Decatur?
Decatur receives around 2,660 hours of sunshine per year. July is the sunniest month with 320 hours, while December is the cloudiest with just 129 hours. Overall, Decatur enjoys abundant sunshine.
Decatur 3-Day Forecast
Decatur (IL) 3-Day Forecast
Decatur on the map
Decatur is highlighted — select any city to see its climate.
Popular this month
Where to go in July — average daytime high across popular destinations.
Bucket list
Need travel inspiration? Check out our bucket list articles and be inspired.
Yosemite National Park is definitely worth a visit
Vast forests, blue lakes, towering sequoias, and majestic waterfalls hint at the beauty of Yosemite National Park—a true natural masterpiece.
The 10 most alternative cities in the United States
Discover the top 10 fun and alternative U.S. cities rich in art, culture, and adventure. From Portland's hippy charm to Sedona's stunning landscapes.
Sedona: Explore Majestic Red Rock Landscapes
A picturesque artists' town surrounded by red rocks and known for its spirituality, vortex energy, and stunning hikes like Cathedral Rock.
10 most idyllic villages to visit in the United States
Discover 10 idyllic villages in the USA, from California to Vermont. Explore their unique charm, rich history, stunning nature, and vibrant arts scenes.