Tornadoes, often associated with the Great Plains, can affect many regions, including large metropolitan areas. The Chicago metropolitan area, like other parts of Illinois, experiences these powerful storms. While less frequent than in some areas farther south or west, tornadoes do occur within Chicago and its surrounding suburbs.
Tornado Activity in the Chicago Metropolitan Area
The Chicago metropolitan area has a history of tornado occurrences. Between 1855 and 2008, 92 significant tornadoes were recorded across the eight-county Chicago metro area. Illinois averages approximately 35 to 54 tornadoes annually.
These storms are most common during the spring months, from March through June, with a secondary, smaller peak observed in late summer to mid-fall. Tornadoes in the region are most frequent from early afternoon into the evening, often peaking between 5:00 PM and 6:00 PM. Historical data indicates that the period from the 1950s through the 1970s was particularly active for tornadoes in the Chicago area.
Several past tornado events stand out due to their impact. On April 21, 1967, an F4 tornado struck Palos Hills, traveling through Oak Lawn and into the south side of Chicago, resulting in 33 fatalities in Cook County and 500 injuries. Another event occurred on August 28, 1990, when an F5 tornado, the only one of its intensity to hit the Chicago area, formed near Oswego and moved through Plainfield, Crest Hill, and Joliet. This storm caused 29 deaths and 350 injuries, along with an estimated $165 million in damage. More recently, on June 20, 2021, an EF3 tornado impacted the suburbs of Naperville and Woodridge, injuring 11 people.
Understanding Chicago’s Tornado Environment
Chicago’s position within Illinois places it in a region susceptible to severe weather patterns common across the Midwest. Illinois ranks fifth nationally in terms of tornado frequency per 10,000 square miles. These storms are often fueled by warm, moist air originating from the Southern United States.
The proximity of Lake Michigan introduces a unique dynamic to local weather patterns. While some believe the lake offers protection, this is a misconception, as tornadoes have indeed struck within Chicago’s city limits. The cooler air from Lake Michigan can sometimes weaken thunderstorms as they approach the shoreline. However, under different atmospheric conditions, the lake breeze boundary can also act to initiate or intensify storm development.
The urban landscape itself can also play a role in local weather. The urban heat island effect, where cities are warmer than surrounding rural areas due to less vegetation and more heat-absorbing surfaces, can influence atmospheric conditions. While this effect can increase the likelihood of tornadoes in urban areas, it does not make cities immune to these storms.
Staying Safe During Tornado Events
Being prepared for a tornado event is an important aspect of living in the Chicago metropolitan area. Developing a family emergency plan is a practical step, ensuring everyone knows what to do and where to go when severe weather threatens. This plan should include having an emergency kit readily available, stocked with essential supplies such as water, non-perishable food, flashlights, and a first-aid kit.
Identifying a safe place within your home is important. Basements or storm shelters offer the highest degree of protection. If a basement is not available, the safest alternative is an interior room or hallway on the lowest floor of a sturdy building, away from windows. When a tornado warning is issued, avoid windows and crouch under sturdy furniture to protect yourself from falling debris.
For those caught outdoors or in a vehicle during a tornado warning, seeking immediate shelter in a sturdy building is advised. Never attempt to outrun a tornado in a vehicle, and avoid seeking shelter under highway overpasses, as these offer no safety. If no sturdy shelter is accessible, lying flat in a low-lying area, such as a ditch, and covering your head can provide some protection. Staying informed through NOAA Weather Radio, local news, and smartphone alerts is also important, as the City of Chicago utilizes outdoor warning sirens to alert residents.