The United States saw its third 1-in-1,000-year rain in a week on Monday night and Tuesday morning, as southern Illinois was drenched by 8 to 12 inches of rain in 12 hours. An area just south of Newton, Ill., recorded 14 inches of rainfall in just 12 hours, according to the National Weather Service. Thunderstorms brought damaging winds and heavy rainfall through midafternoon on Tuesday.
Heavy rain events such as this are becoming more common due to climate change.
The NWS office in Lincoln, Ill., received about 20 reports of flooding on Tuesday, as roads turned into rivers. Several flash flood warnings were issued in the region.
The extraordinarily heavy rain in Illinois comes on the heels of similar events in Kentucky and Missouri. Record-breaking rainfall caused flash flooding in the St. Louis area last Tuesday, trapping cars, closing roads and causing at least one death. Last Thursday, rural areas of eastern Kentucky were flooded after receiving up to 14 inches of rainfall. The death toll, at the most recent count, stood at 37.
Although more rain actually fell in Illinois on Tuesday morning — a foot in the area southeast of Springfield, Ill., for example — the flooding was worse in St. Louis because urbanized areas are more heavily paved and less able to absorb water.
All three inundations are considered 1,000-year rain events because the amount of rain that fell during such a short window has only a 0.1% chance of happening in any given year.
But that was before climate change. Due to rising concentrations of heat-trapping gasses, mainly from the combustion of fossil fuels, the global average temperature has increased by 1.1 degrees Celsius (2 degrees Fahrenheit) since the dawn of the Industrial Revolution. With each degree Celsius of increased temperature, the air can hold 7% more moisture. Therefore, unusually heavy rains are becoming more frequent and severe.
This is especially true in the already-wet Northeast and Midwest. Last year, the Detroit area got 6 inches of rain in June and 8 inches in August, flooding basements and cars, and Hurricane Ida dumped more than 3 inches of rain on New York City in just one hour, resulting in flooding that killed 11 people and shut down the subway system.
Academic studies have shown that extreme rainfall and flooding will get worse in the future, especially if climate change continues unabated.