HOUSTON — Forecasters warned Monday that more than 2 million people lie in the path of a series of storms that could produce an outbreak of violent, large-scale tornadoes across parts of Texas and Oklahoma, along with baseball-size hail, flash flooding and hurricane-force winds.

The warning, issued by the National Weather Service’s Storm Prediction Center in Norman, Oklahoma, forecast a “major severe weather outbreak” on Monday over parts of northwest Texas and western and central Oklahoma. By early Monday evening, scattered tornadoes briefly touched down in largely rural areas in southwest and north-central Oklahoma, causing some damage but no reported injuries or fatalities.

But the National Weather Service warned that “the threat for more tornadoes remains high with this storm” in Oklahoma. In the north-central part of the state, local television crews captured images of two twin tornadoes in a rural region near the small town of Crescent. In the southwestern corner of the state near the Texas border, a tornado appeared to strike some homes near Mangum, a town of 3,000 more than 150 miles from Oklahoma City.

National Weather Service forecasters posted a message on Twitter shortly after 5 p.m., warning about that tornado near Mangum. “Take cover NOW!” a forecaster wrote in the tweet.

As part of the warning issued earlier Monday, the Storm Prediction Center took the rare step of announcing a “high risk” zone for potentially catastrophic tornadoes, the first time in two years that the center had designated such an area. Numerous cities and towns were placed in the high-risk zone, including the Texas towns of Childress, Haskell and Snyder, as well as Oklahoma City, Norman, Lawton and Moore in Oklahoma.

In 2013, a deadly tornado devastated Moore, a suburb just south of Oklahoma City, destroying an elementary school and killing several students inside. That tornado carved a destructive path in the region for 17 miles and killed 24 people, including 10 children. The timing of the warning was particularly ominous for residents of Moore: Monday was the six-year anniversary of the tornado that struck the town.

On Monday, several school districts in Oklahoma, including in the Oklahoma City and Tulsa regions, canceled classes. Other residents and agencies were taking their own precautions. Tinker Air Force Base, near Oklahoma City, evacuated some aircraft.

The office of the Oklahoma governor, Kevin Stitt, said in a statement that the state’s emergency operations center had been activated and that an advance team from the Federal Emergency Management Agency had been brought in to “help facilitate the delivery of any federal resources that may be needed.”

In a brief video posted on Twitter, a National Weather Service forecaster said to expect “multiple waves of severe thunderstorms,” adding, “Do not let your guard down on Monday night. It looks like severe storms and flooding will still be a big problem overnight.”

2019 New York Times News Service