When planning a visit to Illinois in the United States of America, it helps to know that temperatures typically range from 0°C (32°F) in January up to 29°C (84°F) during the peak of July. Our detailed climate overview is based on data from Chicago, the region's most well-known city. For more detailed climate information about other cities in the area, please see the section beneath the map further down the page.
In Illinois, the months of May, June and September bring pleasant weather, with average temperatures ranging between 21°C (70°F) and 26°C (79°F).
The colder weather is most prominent in the months of January, February, March, November and December.
When it comes to rainfall, Illinois sees significant variations throughout the year. June tends to be the wettest, receiving 125 mm (4.9 in) of rain, while January is much drier with just 50 mm (2 in).
Visitors hoping to maximize their time in the sun should consider planning their trip for July, when daylight hours are at their peak.
