What’s the climate like in Illinois?
The current climate of Illinois features average monthly temperatures ranging from highs of 29°C during the day to lows of 1°C. The average yearly temperature is around 18°C. At night, temperatures in the colder months average around -7°C and in the warmer months around 19°C.
The highest temperature recorded in Illinois in recent years was 37°C in August 2023. The lowest daytime temperature recorded was -22°C in January 2014.
On average, Illinois gets 955 mm of precipitation each year. Of this, about 59 cm is snowfall. For comparison, UK gets 701 mm of precipitation each year.
The climate of Illinois is based on weather data from . Other spots, like New York City, Miami or Los Angeles, might have different weather. You can check out all destinations in Illinois for a full picture of the climate.
Best time to visit Illinois?
The best time to visit Illinois for sunny weather is May through October. During this period, you'll have good temperatures and not too much rain, making it a great time to visit Illinois. In the other months of the year, there's too much rain or the temperature isn't ideal for a visit if you want sunny and pleasant weather.
Climate Table of Illinois
The climate table of Illinois shows the average temperatures, precipitation, snow, and UV index per month. The table gives an overview of the average day and night temperatures in degrees Celsius, the total amount of precipitation in millimetres, the total snowfall in centimetres, and the UV index for each month. Precipitation is always measured as water, even if it's snow or hail.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Temp. max (°C) | 1 | 5 | 10 | 17 | 24 | 29 | 29 | 29 | 27 | 19 | 11 | 5 |
| Temp. min (°C) | -7 | -5 | 1 | 6 | 13 | 18 | 20 | 19 | 16 | 9 | 1 | -2 |
| Precipitation |  |
|
|
|
|
|
|
|
|
|
|
|
| Precipitation (mm) | 44 | 77 | 70 | 88 | 99 | 109 | 96 | 92 | 80 | 94 | 51 | 55 |
| Snow (cm) | 16 | 23 | 6,4 | 1,5 | 0 | 0 | 0 | 0 | 0 | 0,7 | 5,0 | 6,3 |
| UV Index | 1 | 2 | 2 | 2 | 2 | 3 | 2 | 1 | 2 | 2 | 3 | 1 |
Click on the month name to see more weather details, like daily averages, temperatures, and precipitation for the past years in that month.
- Average yearly temperature: 18°C
- Highest temperature: 29°C in June, July and August
- Lowest temperature: 1°C in January
- Precipitation*: 955 mm per year, averaging 80 mm per month
- Snowfall: 59 cm per year
- Driest months: 44 mm in January, 51 mm in November and 55 mm in December
- Wettest months: 109 mm in June, 99 mm in May and 96 mm in July
*Precipitation is measured as a combination of rain, snow, and hail
Plan your next holiday
Don’t miss the best holiday deals for Illinois and see what our partners have for you.
Table of Contents
Average Temperature per Month in Illinois
This graph shows the average maximum temperatures per month in Illinois, United States. The temperatures are shown in degrees Celsius and the average is calculated based on the recorded temperatures per month from past years.
Average Precipitation per Month in Illinois
This graph shows how much precipitation Illinois, United States, gets on average per month. Precipitation is always measured as water, even if it's snow or hail. This makes it easy to compare how much has fallen, regardless of the form of precipitation. The amount of precipitation is measured in millimetres and the average is calculated based on the recorded precipitation per month from past years.
Average Snowfall per Month in Illinois
This graph shows how much snow Illinois, United States, gets on average per month. The amount of snowfall is measured in centimetres and the average is calculated based on the recorded snowfall per month from past years.
Average UV Index per Month in Illinois
This graph shows the average UV index per month in Illinois, United States. The UV index indicates the intensity of ultraviolet radiation and ranges from 0 to a maximum of 11.
Yearly Temperature in Illinois
This graph shows the average yearly temperature in Illinois, United States. The yearly temperature, expressed in degrees Celsius, is the average of all twelve monthly temperatures summed up for that year.
Total Yearly Precipitation in Illinois
This chart shows the total yearly precipitation in Illinois, United States, over the past few years. The total yearly precipitation, measured in millimetres, is the sum of all the rain that fell in the twelve months of that year.
Total Yearly Snowfall in Illinois
This chart shows the total yearly snowfall in Illinois, United States, over the past few years. The total yearly snowfall, measured in centimetres, is the sum of all the snow that fell in the twelve months of that year.
Weather experiences in Illinois
Have you been to Illinois?
Share your weather experiences in Illinois.
Average Weather in Illinois by Month
Click on a month below to see detailed weather info for Illinois. Based on historical weather data, you can see the average temperature, precipitation, wind, and UV index for each day of the month.
Popular destinations in United States
Discover the climate of these popular destinations in United States.
