Tornadoes have struckChicago multiple times. Chicago, the largest city in Illinois and the third largest in the United States, lies in an area susceptible to severe weather year-round, with theRomeoville National Weather Service office providing continuous severe weather outlooks for Chicago and surrounding regions. The city has been struck by multiple tornadoes, including the devastatingOak Lawn tornado which struck theSouth Side in 1967, and amultiple vortex tornado that struckthe Loop in 1876. Studies of tornadoes in the region show that asChicago's suburbs grow, they become more susceptible to tornadoes, with the strongest tornado in the region strikingPlainfield in 1990. Chicago was also the home of the severe weather researcherTed Fujita, a professor at theUniversity of Chicago, who extensively contributed to the scientific model of the tornado. The first tornado on record in Illinois, which struck modern-dayDes Plaines, led to correspondence between a Chicago newspaper and theSmithsonian Institution, the efforts of which across the country eventually gave rise to the creation of theNational Weather Service.

A regional myth states thatLake Michigan protects Chicago from tornadoes; this is not true, and while the relatively cooler air coming off the lake can influence some tornadoes, others have been seen forming near the lakefront and some have moved over the lake itself.^[1] Another myth states that urban development andChicago's tall buildings protect the city from tornadoes; buildings have a negligible effect on the formation and path of a tornado.^[2]

Ted Fujita was the lead figure for tornado science and research, and was a professor at theUniversity of Chicago.^[3] His research included comparing theintensity of tornadoes to the damage patterns of theatomic bombings of Hiroshima and Nagasaki, furthering the theory of thedownburst pattern of damaging winds, and developing theFujita scale for ranking tornadoes based on the damage they cause.^[4] Following the Plainfield tornado in 1990, Fujita said that a tornado in theChicago Loop, the most developed part of the city, couldn't be ruled out:

We should not assume a false sense of security in our city ... A large, violent tornado might manage to smash through the Loop, damaging skyscrapers and causing showers of window-glass onto the streets.^[5]

A study by National Weather Service Chicago, Illinois found that a violent (F4–F5)^[a] tornado strikes the Chicago metropolitan area on average once every 9.8 years, with F3 and F2 tornadoes much more common at once every 4.5 and 1.3 years on average respectively. A majority of both deaths and injuries caused by tornadoes in the area were the result of F4 tornadoes, with a large amount of total fatalities in the region originating on just three days – March 28, 1920, April 21, 1967, and August 28, 1990. The study concludes by stating that "[t]he Chicago area is overdue for a major tornado", while also mentioning that, as rural areas are developed into populated places, more people are at risk of the impacts of a tornado.^[6]

In a second study analyzing local storm reports between 2001 and 2020, the National Weather Service determined the time of year when severe weather happened based on the amount of days on which a severe weather report occurs in the Chicago region. The study found that there are on average three days with reports of severe weather between the months of May and August, with tornado days specifically occurring most commonly in May and June. Days with damaging wind events were found to be most common in June and July. Severe weather typically occurs between 1 and 9 p.m. local time, with tornadoes being especially common between 4 and 8 p.m. local time. The study also found that only about 5% of tornadoes in the region are rated F3 or higher, with only 1.6% being rated F4 to F5. An apparent increase in tornado reports between 1960 and 2020 was attributed to increased access to electronic means to report severe weather, a higher population in the Chicago andRockford metropolitan areas, and the rise oftrained volunteer storm spotters. An apparent decrease in the amount of days with significant tornadoes, those rated F2 or above, from about two every year to only one, was attributed to improved building codes.^[7]

A 2014 study by Ashley et al. attempted to quantify the increasing risk of a tornado based on the development of suburban and exurban areas in the Chicago area using synthetic tornado paths, influenced by historical tornadoes including the2011 Joplin tornado. A hypothetical "worst case" scenario was determined to impact as many as 200,000 people with direct tornadic intensity, whereas the overall population at risk of a tornado was increasing significantly with time, especially expanding high-density suburban development in theChicago metropolitan area, in what was dubbed an "expanding bull’s-eye effect". The highly dense risk exposure that exists in Chicago's central business district could pose a "catastrophic disaster potential" due to critical infrastructure being overwhelmed.^[8]

Chicago and surrounding areas are under the coverage ofNational Weather Service Chicago, Illinois, aNational Weather Service office located inRomeoville on the grounds ofLewis University Airport. The National Weather Service also operates a Center Weather Service Unit inAurora for the purposes of aviation. The forecast office, when fully staffed, has 13 or 14 employees, but only have 2 or 3 at any given time, who monitor Chicago-area weather all hours of the day. The number of active forecasters can be increased before a significant event. The National Weather Service works alongside local emergency management to relay warnings and other relevant information, and data from the service is used bybroadcast meteorologists on local television across the region.^[9]

WGN forecaster Mark Ratzer determined in 2018 that areas under the jurisdiction of the Chicago National Weather Service office are on average put undertornado watches on 6 days every year, with a further 15 days having asevere thunderstorm watch.^[10]

Cook County's hazard mitigation plan discusses the hazard of tornadoes, discussing their potential to have significant impacts in the "Safety and Security" and "Health and Medical" fields. Cook County had 15,345 manufactured homes (as of 2024), which are the structures most vulnerable to the impacts of a tornado. The total exposure of all structures vulnerable to a tornado was over $893 billion dollars (2022 USD). TheFederal Emergency Management Agency assigned Cook County a "Very High" social vulnerability score for tornadoes, and assigned a risk index of 100 for all tornadic events.^[11]

External videos
Tornado Sirens in Downtown Chicago, (23 June 2010)

As of 2025, Chicago has a total of 112warning sirens across the city; these are split into 12 siren zones. Sirens may be activated individually, by zone, or city-wide. Sirens are tested for 30 seconds on the first Tuesday of every month at 10:00 a.m. local time. Sirens are sounded during tests andtornado warnings, alongside earthquakes, biological hazard incidents, extreme wind events, and generalsevere weather.^[12]

In 2022,F Newsmagazine wrote that the sound of tornado sirens in Chicago is distinct compared to many others, containing bothrising and falling tones alongside a third tone drop. It has been compared to a malfunctioningambulance siren, with the host ofNews Center Maine stating that[i]f there is anything creepier than a tornado it’s this. The sound is produced by theFederal Signal Modulator model of siren's "alternate wail" mode. It was chosen to distinguish the sound of warning sirens from those of emergency vehicles.^[13]

A potential tornado occurred in theChicago Portage region in the modern-day southwest of Chicago in 1781, where a traveller reported significant tree damage near Mud Lake. This may have been the first tornado in the Chicago region, however, this event is officially not acknowledged by the National Weather Service.^[14]

A tornado struck downtown Chicago on May 6, 1876, killing 2 and injuring 35 across its 4 mi (6.4 km) path. Structures damaged or destroyed include the Reaper Mansion, a candy factory, a county hospital, and a freight depot. A reporter with theChicago Tribune published a description of the tornado'smultiple vortex structure, well ahead of accepted scientific theories on the subject:^[15]

[I]t was then composed of eight or ten columns grouped together, all whirling around a central point. The columns, or spirals, twisted and writhed like snakes. The group was about 500 feet in diameter, the various parts leaning at the top towards the centre, and bulging slightly at the middle. Now and then a column would draw away from its fellow and then sweep back. The down rush of air in the vacuum drew the cloud down. Directly under the mass the lake was flat and still. Around it the waters were lashed and torn. The waves dashed upon the spirals as if driven to madness by the attack. As the pillars curled around, binding themselves together, the cloud vomited lightning, as though sick of the performance. Another such scene may never come in this generation, and it is to be regretted that the cylinder could not have been caught and pickled for scientific investigation.^[16]

While workers at the freight depot and the county hospital were trapped, they survived the tornado.^[15] WGN meteorologistTom Skilling brought up the 1876 tornado as a response to a query about a tornado striking high-rises in downtown Chicago, despite its occurrence well before the construction of Chicago's high-rise buildings.^[17]

The Oak Lawn tornado occurred on April 21, 1967 and was described as the "worst storm of the day" during the1967 Oak Lawn tornado outbreak. The tornado struckOak Lawn where numerous homes were leveled. At the intersection of 95th Street and Southwest Highway, traffic led to numerous stopped cars being lofted into the air and dispersing in all directions. The tornado leveled a roller skating rink and mobile home park before strikingHometown andEvergreen Park. The tornado moved through Chicago'sSouth Side, where the tornado widened and moved onto Lake Michigan near a water filtration park at 78th Street, where a wind gust of 100 mph (160 km/h) was recorded.^[18]

Following the tornado, PresidentLyndon B. Johnson deployed 800 National Guard troops to Oak Lawn to aid in search-and-rescue operations.^[18] A later analysis of interviews following the tornado found that, while a majority of people in houses were sheltering in basements or in the process of doing so, many of those affected by the tornado had been away from home, in places where they would be unable to receive any warning of the tornado. Ahead of the storm, following the issuance of atornado warning forMcHenry county for theF4 Belvidere tornado, the Weather Bureau's warnings were extended for DuPage, Kane, and Cook counties, 24 minutes before the Oak Lawn tornado touched down, in what was described as "an outstanding example of the Weather Bureau’s Tornado Warning System"^[19]

A series of storms, including a potentderecho, impacted the Chicago region on July 14 and 15, 2024, producing two notable tornado events concentrated in the region, with as many as 5 tornadoes ongoing concurrently. Notably, 6 tornadoes directly impacted the city of Chicago; in addition to the numerous others from the Chicago National Weather Service office, the totals stood at 32 from the July 15 event; 35 on the calendar date of July 15, including those from overnight on July 14; 38 in the 24-hour period from 10:20 p.m. from July 14 through July 15; all records for the Chicago National Weather Service office's area of responsibility (with modern record-keeping beginning in 1950). Similar records were broken for the entire state of Illinois during the event. The anomalously high tornado figure was noted as far exceeding the longstanding record of 32 in a single calendar year, a figure broken the previous year,2023, in which 58 tornadoes were recorded to strike the region. In addition, the average amount of tornadoes to strike the region in the month of July was only 1, using 10 to 20-year climate records. Storms of a similar magnitude to the July 15 derecho were described as being such that the Chicago region would experience them every 5–10 years or so.^[20]

The record-breaking amount of tornadoes during the event was attributed to three primary factors: increased understanding of tornado-producing weather systems; better detection of tornadoes via radar; and better surveying and volunteer reporting methods. The Chicago National Weather Service office conducted storm surveys for weeks after the event and determined the figure of 32 from the July 15 event primarily consisted of EF0 and EF1 tornadoes, with only one EF2 tornado occurring during the entire event.^[20]

The earliest recorded tornado inIllinois struck near the town of Jefferson on May 22, 1855. The tornado struck in the afternoon between 3 and 5 p.m. local time, and lifted a granite house off of its foundation, killing three.^[21] The exact location of this tornado has been the subject of confusion, with earlier records confusing the community of Jefferson with a town inJefferson Township, which would later be annexed as theJefferson Park neighborhood of Chicago. The location reported as "Jefferson" was later discovered to be in present-day Des Plaines, on property owned by the Jefferson family, with confusion attributed to initial reporters on theIllinois and Wisconsin Railroad which stopped in the aforementioned township.^[14]Joseph Henry of theSmithsonian Institution corresponded with theDaily Democratic Press in Chicago for more information about the tornado and its effects that June, and the Smithsonian's organized efforts to record weather information across the United States would lead to the creation of theUnited States Weather Bureau, now known as the National Weather Service.^[21]

Elgin andLake Zurich were struck by an F4 tornado on April 21, 1967, which tracked 17 mi (27 km) across parts ofKane,Cook, andLake counties.^[c] The tornado removed the roof at a factory and caused $100,000 in damage (1991 USD, $231,000 adjusted) to a hospital in Elgin, before growing in size and intensity and destroying 500 homes across Lake Zurich. Through Barrington Hills, homes were leveled, and cars were "thrown like toys" at the intersection ofRoute 22 andRoute 59. In all, 123 were injured, with the total damage cost coming to $10,000,000 (1991 USD, $23,086,000 adjusted).^[22]:483

An F4 tornado moved fromNorth Chicago toWaukegan on September 28, 1972. This was recorded by the National Weather Service as having a 5 mi (8.0 km) long path, causing 20 injuries and $1 million of damage.^[23] Grazulis records this as an F2 tornado family, only causing 3 injuries, with $30 million (1991 USD, $69,257,000 adjusted) of damage.^[22]:527

On June 13, 1976, an F4 tornado following an unusual path struckLemont,Darien, and an area corresponding to modern-dayDowners Grove. In Lemont's Hillcrest subdivision, homes were severely damaged, vehicles were lofted, and numerous trees were uprooted, with the area being described as being "left looking like a war-torn battlefield". The tornado would go on to destroy electrical infrastructure as it struck and tore the roof off ofArgonne National Laboratory's Biology wing, which, at the time, housed anuclear reactor. Overall, 2 were killed and 23 were injured by the tornado.^[24]

The strongest tornado in theChicago metropolitan area struck the suburbs ofPlainfield andJoliet on August 28, 1990. This was the only tornado rated F5 or equivalent, the highest rating on theFujita scale, in the region. The tornado was particularly deadly as it lacked atornado warning - as a result, it killed 29 and injured 350 over its half-hour lifespan. The tornado damaged 1000 homes and destroyed a further 470 and produced a total of $160 million (1990 USD, $385,084,000 adjusted) in damage.^[25] Ted Fujita stated that Joliet has an unusually high concentration of strong tornadoes, but was unable to state why.^[5]

A large EF3 tornado moved through the western suburbs ofNaperville,Woodridge, andDarien, at 11:02 p.m. on June 20, 2021. This tornado primarily affected areas of southern DuPage county, enteringBurr Ridge andWillow Springs in Cook County near the end of its life. The tornado downed thousands of trees and injured 10 across its 17.6 mi (28.3 km) path, but despite moving through densely populated areas well after dark, relatively few injuries occurred; this was attributed by the National Weather Service to be partially due totornado preparedness and the improved usage of tornado warnings before storm events.^[26] Over a year later, residents of Naperville were still dealing with the effects of debris in the topsoil, which was the subject of the non-profit organization Naperville Tornado Relief's primary efforts.^[27]

This list contains all tornadoes of any intensity to strike within the city limits of Chicago, and any tornado rated F2 or above in the Chicago metropolitan area. This list only includes thecollar counties and Lake County, Indiana. Other counties that may be considered part of the Chicago metropolitan area are not included.

• List of Illinois tornadoes
• Climate of Chicago
  • June 2022 Chicago supercell, a record-breaking thunderstorm that impacted the region
• List of tornadoes in Washington, D.C.
• St. Louis tornado history

• Tornadoes in Illinois

• Source attribution
• Wikipedia semi-protected pages
• Articles with short description
• Short description with empty Wikidata description