Weather by month in Illinois

Illinois is a region in the United States of America. Many people wonder what the weather conditions are in Illinois over the year. What is the best time to visit Illinois?

This page shows the average weather conditions by month in Illinois over the year in: January, February, March, April, May, June, July, August, September, October, November, December.

In January the weather in Illinois is generally poor. January is a winter month. The temperatures range from very low in Galena with -2°C to low in Metropolis with 6°C. On average, this month is one of the coldest months of the year in Illinois. So be prepared and make sure to dress up warm.

Find more detailed climate information for Illinois in January here.

In February the weather in Illinois is generally poor. February is a winter month. The temperatures range from very low in Galena with -2°C to low in Metropolis with 7°C. It is a very cold month in some areas, so be prepared and make sure to dress up warm.

Find more detailed climate information for Illinois in February here.

In March the weather in Illinois is generally poor. The temperatures range from low in Roscoe with 5°C to moderate in Metropolis with 15°C.

Find more detailed climate information for Illinois in March here.

In April the weather in Illinois ranges from poor in Waukegan to tolerable in Joliet. The temperatures range from low in Zion with 12°C to pleasant in Metropolis with 21°C.

Find more detailed climate information for Illinois in April here.

In May the weather in Illinois ranges from pleasant in Chicago to perfect in Freeport. The temperatures range from pleasant in Zion with 18°C to high in Metropolis with 25°C.

Find more detailed climate information for Illinois in May here.

In June the weather in Illinois is generally pleasant. June is a summer month. The temperatures range from high in Roscoe with 23°C to very high in Metropolis with 31°C.

Find more detailed climate information for Illinois in June here.

In July the weather in Illinois ranges from pleasant in Chicago to perfect in Waukegan. July is a summer month. The temperatures range from high in Roscoe with 26°C to very high in O'Fallon with 31°C. On average, this month is one of the warmest months of the year in Illinois. So be prepared and make sure to dress lightly.

Find more detailed climate information for Illinois in July here.

In August the weather in Illinois ranges from pleasant in Chicago to perfect in Waukegan. August is a summer month. The temperatures range from high in Roscoe with 24°C to very high in Metropolis with 31°C.

Find more detailed climate information for Illinois in August here.

In September the weather in Illinois ranges from pleasant in Schaumburg to perfect in Chicago. The temperatures range from pleasant in Roscoe with 21°C to high in Metropolis with 28°C.

Find more detailed climate information for Illinois in September here.

In October the weather in Illinois ranges from tolerable in Chicago to pleasant in Peru. The temperatures range from moderate in Roscoe with 14°C to pleasant in Metropolis with 21°C.

Find more detailed climate information for Illinois in October here.

In November the weather in Illinois is generally poor. The temperatures range from low in Roscoe with 8°C to moderate in Metropolis with 14°C.

Find more detailed climate information for Illinois in November here.

In December the weather in Illinois is generally poor. December is a winter month. The temperatures range from very low in Galena with 1°C to low in Metropolis with 9°C. It is a very cold month in some areas, so be prepared and make sure to dress up warm.

Find more detailed climate information for Illinois in December here.