Millions of Americans under threat of tornadoes as spring storm season kicks in early in the US

Concern is rising that the first major storm outbreak in the run-up to spring could strike the nation's heartland, putting millions of Americans from Texas to Iowa at risk of potentially strong tornadoes.

Some scattered severe thunderstorms were expected to begin firing up late Thursday in the Texas Panhandle and across western Oklahoma and parts of Kansas, the National Weather Service said. Large hail, damaging winds and possibly a few tornadoes were also expected, according to the forecasters.

But the strongest storms were expected Friday in a zone that includes much of Oklahoma, Kansas and Missouri and extends into some nearby states, according to weather service projections.

More than 6 million Americans are at the highest risk of severe weather Friday in an area that includes the metropolitan areas of Kansas City and Tulsa, Oklahoma, according to the national Storm Prediction Center. Another 22 million people are at a slightly lesser risk in a zone that includes Oklahoma City; St. Louis; Omaha, Nebraska; and Milwaukee, Wisconsin.

The weather pattern that's bringing the potential for strong storms is also expected to usher in extremely warm temperatures for this time of year by the weekend.

“Temperatures will be 20-30 degrees above average, with 80s reaching as far north as parts of the Ohio Valley and Mid-Atlantic,” federal forecasters wrote in their long-range forecast discussion. “Daily records could become widespread.”