Scattered vigorous thunderstorms accompanied by frequent cloud-to-ground lightning and localized downpours moved across the Chicago area Wednesday evening bringing what, up to that point, were welcome rains (though Lake and McHenry Counties to the north missed the action). Then, quite unexpectedly, thunderstorms expanded across Cook County and became real rain-producers by 8 pm, putting down rain at a rate exceeding two inches per hour. Rain totals exceeded three inches in eastern Cook County by the time thunderstorms moved out of the area. Much cooler and drier air of Canadian origin arrives Friday, but not until Thursday’s readings flirt with 90 degrees. Additional thunderstorms are likely Thursday afternoon and night in advance of the Canadian air, but, once here, that Canadian air mass ends the rain threat for the area for at least a few days.