ST. LOUIS (AP) - The latest update on the nation's drought shows that the parched conditions continue worsening in key farm states even as the situation across all of the continental U.S. leveled off. The weekly U.S. Drought Monitor map shows that nearly all of Nebraska and Missouri are in extreme or exceptional drought, narrowly ahead of Illinois and Kansas in those two categories. The amount of Nebraska afflicted with exceptional drought conditions - the most-serious level - remained unchanged while dropping only slightly in Illinois. The map also shows that more than two-thirds of Iowa, the nation's biggest corn producer, was suffering extreme or exceptional drought - the worst two classifications - as of Tuesday. That's up more than 5 percentage points from last week, despite cooler temperatures.