Climate and Weather of Illinois, the United States of America

In the United States of America you have several regions, one of which is called Illinois. The most popular city in this region is Chicago, whose climate data we'll examine to provide you with an overview of what weather to expect in Illinois. For detailed climate information about other cities in the area, please refer to the section beneath the map further down the page.

In Illinois, during the months of May and September you can expect comfortable weather, with average temperatures ranging from 20°C to 25°C. On average, the warmest month(s) are July and August. The coldest month is January with an average maximum temperature of 0°C. However, the specific temperature can vary depending on the exact location within the region.

Additional climate insights:

• The coldest season / winter is in the months of January and February.
• June is the wettest month in Illinois. This month should be avoided if you are not a big fan of rain.
• January is the driest month.
• The warmest month in Illinois is July with an average maximum temperature of 28°C.
• The coldest month is January with an average maximum daytime temperature of 0°C.
• July is the sunniest month in Illinois.

Interested in the detailed Weather and Climate of Illinois, the United States of America?

Please select a city below the map you wish to travel to, or the one closest to your destination. Each selected city will show you the following graphs:
1. Average minimum and maximum temperature over the year
2. Average monthly precipitation over the year (rainfall, snow)
3. Average monthly hours of sunshine over the year
On certain pages we also offer other historical climate data like humidity wind speed and water temperature.