Over 60 million Americans could be in the path of severe storms moving across the country. A low-pressure system traveling from Montana across an 1,800-mile swath of the country that stretches all the way to the mid-Atlantic coast is causing drenching rains, high winds, and severe thunderstorms.

"These repeated rounds of thunderstorms could produce heavy rainfall on the order of 2-3 inches in a short period of time, elevating the risk for rapidly rising water, including flooding of creeks and streams as well as roadways," AccuWeather Meteorologist La Troy Thornton said.

Parts of South Dakota have already seen wind gusts up to 96 mph and hail the size of a tennis ball. Forecasters said the storms could intensify as they interact with a powerful heat dome settled over portions of the country.

That could cause the storms to develop into a derecho, a massive windstorm that can cause damage across an area at least 60 miles wide and 400 miles long.

"One of the unique aspects of this type of severe thunderstorm setup is that the threat for wind damage is much more widespread than what typically occurs with most severe thunderstorms," Thornton explained. "Typically, severe thunderstorm wind damage tends to be much more localized to a part of a community, whereas this cluster of thunderstorms may create widespread damage over a much larger area."

By Wednesday (July 6) and Thursday, the storm system is expected to bring severe weather to other cities, including Chicago, Cincinnati, Washington, D.C., and Columbia, South Carolina.

Need to Know with Jeff Angelo