July 23, 2011 – CHICAGO – Those looking for some kind of a break from the heat of the last week got it overnight — a rainstorm that dropped temperatures into the low 70s. But like the heat wave that preceded it, this rainstorm was anything but ordinary. According to ChicagoWeatherCenter.com, the total rainfall at O’Hare — 6.91 inches as of about 6:50 a.m. — is the largest single-day rainfall since records began in 1871. The highest previous daily total was 6.64 inches on Sept. 12, 2008. And more rain is on the way. There were rainfall totals as high as 7 inches as the storm moved noisily through the Chicago area after midnight, resulting in flash flood warnings from the National Weather Service and enough flooded roads and highways to make life miserable for passengers headed to or from O’Hare International Airport and make a mess of traffic overnight and into Saturday morning. The flash flood warning is in effect until 1:30 p.m. Saturday for most of the northern part of the region, though the rain did end up falling pretty much everywhere. The north side got the brunt of it, though, with O’Hare International airport getting 5.53 inches in two hours, according to ChicagoWeathercenter.com. Some other totals of note reported by the Weather Center: 6.41 inches in Glenview, 5.4 inches in Arlington Heights and 5.49 inches in Elk Grove Village. –Chicago Tribune
Growing phenomenon: We first reported on this phenomenon weeks ago when stories of these storms began pouring in from all around the world. We call them cloudburst storms. They are very intense thunderstorms which, in many occasions, appear to come out of nowhere. Most of these storms develop late at night where the atmosphere has been heated by record daytime temperatures. These storms are characterized by very intense lightning strikes. Some unleash hailstones and monstrous amounts of rainfall which often lead to dramatic flash flooding events. See Cloudburst storms.