The best times to visit Illinois for ideal weather are
April 30th to October 21st
based on average temperature and humidity from NOAA (the National Oceanic and Atmospheric Administration). Read below for more weather and travel details.
Illinois Travel Guide
Other Illinois Travel Info
Weather in Illinois
Average temperatures in Illinois vary drastically. Considering humidity, temperatures feel cold for about half of the year and otherwise nice with a low chance of precipitation most of the year. The area is somewhat temperate — in the 44th percentile for pleasant weather — compared to tourist destinations worldwide. Weeks with ideal weather are listed above. If you’re looking for the very warmest time to visit Illinois, the hottest months are July, August, and then June. See average monthly temperatures below. The warmest time of year is generally mid July where highs are regularly around 86.9°F (30.5°C) with temperatures rarely dropping below 66.5°F (19.2°C) at night.
Illinois Temperatures (Fahrenheit)
Illinois Temperatures (Celsius)
The way we experience weather isn’t all about temperature. Higher temperatures affect us much more at higher humidity, and colder temperatures feel piercing with high winds. Our perceived temperatures factor in humidity and wind chill to better represent how hot or cold the day feels to a person.
Illinois Perceived Temperature (F)
Illinois Perceived Temperature (C)
Average Illinois Temperatures by Month
Daily highs (averaged for the month) usually give the best indication of the weather. A significantly lower mean and low generally just means it gets colder at night.
|Month||Avg. High (°F)||Avg. Mean (°F)||Avg. Low (°F)|
|Month||Avg. High (°C)||Avg. Mean (°C)||Avg. Low (°C)|
Precipitation (Rain or Snow)
If dry weather is what you’re after, the months with the lowest chance of significant precipitation in Illinois are January, February, and then November. Note that we define “significant precipitation” as .1 inches or more in this section. The lowest chance of rain or snow occurs around mid January. For example, on the week of January 15th there are no days of precipitation on average. By contrast, it’s most likely to rain or snow in late April with an average of 2 days of significant precipitation the week of April 23rd.
When can you find snow in Illinois? Weather stations report large amounts of snow likely to be deepest around February, especially close to early February. The best time to ski (if at all) in Illinois is often around around March 26th when fresh powder is deepest. Please note that a value of 0 for snow in the graph below may either mean there was no snow, or that snow is unreported.
Chance of Precipitation
The graph below shows the % chance of rainy and snowy days in Illinois.
Snow on the Ground
The graph below shows the average snow on the ground in Illinois (in).
Average Rain and Snow by Month
|Month||Daily Chance of Rain||Average Snow Depth (in)||Total Precipitation (in)|
|Month||Daily Chance of Rain||Average Snow Depth (cm)||Total Precipitation (cm)|
Humidity and Wind
Illinois has some very humid months, with other comfortably humid months. The least humid month is April (53.5% relative humidity), and the most humid month is December (72%).
Wind in Illinois is usually moderate. The windiest month is April, followed by January and February. April’s average wind speed of around 8.8 knots (10.1 MPH or 16.3 KPH) is considered “a gentle breeze.” Maximum sustained winds (the highest speed for the day lasting more than a few moments) are at their highest in early April where average top sustained speeds reach 17.3 knots, which is considered a fresh breeze.
Relative Humidity (%)
The graph below shows the average % humidity by month in Illinois.
The graph below shows wind speed (max and average) in knots.
Average Wind Speeds
Show Wind Speeds
All wind speeds are in knots. 1 knot = 1.15 MPH or 1.85 KPH.
|Month||Avg. Wind||Avg. Wind Feel||Sustained High Wind||High Wind Feel|
|Jan||8.5||Gentle breeze||15.6||Significant breeze|
|Feb||8.4||Gentle breeze||15.6||Significant breeze|
|Mar||8.3||Gentle breeze||15.6||Significant breeze|
|Apr||8.8||Gentle breeze||17||Strong breeze|
|May||7.3||Gentle breeze||15.1||Significant breeze|
|Jun||6.2||Light breeze||14||Significant breeze|
|Jul||4.9||Light breeze||11.6||Significant breeze|
|Aug||4.5||Light breeze||10.9||Gentle breeze|
|Sep||5.2||Light breeze||11.7||Significant breeze|
|Oct||6.8||Light breeze||13.8||Significant breeze|
|Nov||7.9||Gentle breeze||14.9||Significant breeze|
|Dec||8||Gentle breeze||14.8||Significant breeze|
Show Relative Humidity by Month
|Month||Avg. Relative Humidity|
Is it Safe to Travel to Illinois?
Our best data indicates this area is generally safe. As of Oct 07, 2019 there are no travel advisories or warnings for the United States; exercise normal security precautions. Check this page for any recent changes or regions to avoid: Travel Advice and Advisories. This advisory was last updated on Sep 23, 2019.
The Busiest and Least Crowded Months
The busiest month for tourism in Illinois, United States is June, followed by July and August. Prices for hotels and flights will be most expensive during these months, though you can save if you purchase well in advance. Tourists are unlikely to visit Illinois in December. Those willing to visit at these times will likely find it the least expensive month.
Estimated Tourism by Month
Most Popular Months to Visit
Overall Illinois Travel Experience by Season
Spring (March through May)
Humidity and temperatures combine to make this season feel moderately cold. Highs range from 80.6°F (27°C) and 40°F (4.4°C) with far warmer temperatures in the later months. Rain is somewhat common with 3 to 5 days of significant precipitation per month. Spring is the second busiest for tourism, which makes it a good time for those looking for things to do.
Summer (June through August)
The middle-year months have very comfortable weather with high temperatures that are quite warm. These months see moderate precipitation with 3 to 6 days of precipitation per month. June – August is the busiest season for tourism in Illinois, so lodging and other accommodations may cost more than usual.
Fall (September through November)
Fall daily highs range from 81.9°F (27.7°C) and 46.1°F (7.8°C), which will feel chilly given the humidity and wind. It rains or snows a normal amount: approximately 3 days per month. Tourism is fairly slow during these months due to the weather, so hotels may be lower priced.
Winter (December through February)
Weather is far too cold this time of year in Illinois to be enjoyable for warm weather travelers. The average high during this season is between 41.1°F (5.1°C) and 34°F (1.1°C). On average, it rains or snows a smalll amount: 2 to 4 times per month. These times of year are the slowest with tourists.