A band of severe thunderstorms began lurching eastward Monday across the Great Plains, threatening some 14 million Americans with hail, high winds and tornadoes.
From the Mexican Border north to Lake Superior, the nation's midsection faced at least three days of potentially wicked weather, the National Weather Service warned.
But for all their size and fury, these storms aren't going far, forcasters said.
"It's a large area but it's a stalled front that's not going to move much," Weather Channel senior meteorologist Kevin Roth told NBC News early Monday. "It's going to be a repeated threat this week, possibly into Thursday and even into Friday."
Big cities like Wichita, Kansas, Omaha, Nebraska, and Des Moines, Iowa, were expected to hear the rumble of thunder Monday and get thoroughly drenched, government meteorologists warned.
"Cluster of thunderstorms could also cause some flash flooding," The Weather Channel forecasted.
And large swaths of Oklahoma could be hit with golf-ball-sized hail and winds of up to 60 mph.
"People and animals outdoors will be injured," the NWS warned. "Expect hail damage to roofs, siding, windows and vehicles ... and trees. For your protection, move to an interior room on the lowest floor of a building."
But, he added, "the biggest tornado threat today will come in largely rural areas and low population centers."
On Sunday, at least 27 twisters were reported across Texas, Kansas and South Dakota.
Most touched down in rural areas where cattle far outnumber people, although building damage was reported in Trip County, South Dakota.
What's more, a "large tornado" took down a quarter mile of power lines in Ochiltree Country, Texas, the NWS added.
There were also at least 86 reports of large hail in those states as well as in Nebraska. The largest ice balls were some 3 inches in diameter — the size of a tea cup — and were recorded in Howard County, Texas.
There was also scattered flash flooding, with water as high as 1.5 feet leaving roads impassible in Valentine, Nebraska, according to The Weather Channel.
This latest batch of severe weather started late Saturday, the NWS reported.