All flights bound for O’Hare are grounded until at least 4:45pm Central and likely longer than that. A tremendous line of thunderstorms with winds of 80+mph is just west of O’Hare and will sweep through all of Chicagoland. Midway will have problems, as well. The FAA is predicting average delays of 1.5 hours. However, I don’t think they are giving enough weight to the lightning that will following the winds for at least another hour. Ramp people cannot work with lightning in the area. So, if you can route yourself around O’Hare, tonight would be a good time to do so.
UPDATE: 6:49PM: Chicago Tribune has this photo of the storm (with 77 mph winds) approaching downtown. The Willis Tower (formerly Sears Tower, tallest building in U.S.) had windows blown out. More than 300,000 homes and businesses are without power in Chicago.