An unusual strong storm front is threatening the Midwest from the central Plains to the Mississippi Valley over the next several days.
The National Weather Service's Storm Prediction Center in Norman, Okla., said the system could bring heavy thunder, wind, rain and possibly tornadoes on Friday.
Meteorologist Gregory Carbin said about one-third of Iowa and parts of southern Minnesota have a 45 percent chance of severe storms. More than 1 million people live in that risk area.
Parts of Kansas, Nebraska, Missouri and Wisconsin are also on the storm front's path. Areas as far south as Oklahoma and Texas could be affected.
Meteorologists say this is the first time since at least 2000 that a storm this size in the region has been forecast in October a day in advance.