By Hanna Park and Mary Gilbert, CNN Meteorologist (CNN) — A volatile weather system is poised to unleash severe thunderstorms across the central United States on Sunday, with the potential for tornadoes, large hail and damaging winds. Roughly 170 million people from Illinois to eastern Texas and beyond could be affected over the next two days, as unseasonably warm air collides with a powerful cold front. March has already delivered an extraordinary number of tornado reports, surpassing the number from the same time last year. Some of the same regions struck by deadly storms earlier this month could once again find themselves in harm’s way. Sunday’s threat: golf ball-sized hail and long-lived tornadoes Weekend temperatures from the Plains to the East Coast have felt more like late May or early June, but a cold front coming in Sunday will bring an abrupt end to the unseasonable warmth. As that cooler air collides with the warm, moisture-laden air ahead of it, explosive thunderstorms are expected to erupt. The storms were already spitting out massive hail near Oklahoma City late Saturday. Photos sent to CNN affiliate KOCO show hailstones ranging from about the size of a quarter to a golf ball, many of them spiked. The storms are expected to find a new gear as they sweep east late Sunday afternoon, stretching from Illinois to eastern Texas, and will intensify further as they move eastward through the evening and overnight hours. Forecasters warn Sunday’s storms could bring a range of severe weather, including strong and long-lived tornadoes rated EF2 or higher, hail larger than golf balls and wind gusts strong enough to cause widespread damage. A total of 18.5 million people are under tornado watches, spanning from Indiana to Arkansas. A tornado watch is in effect for portions of northern Arkansas, southern Illinois, southwest Indiana, western Kentucky, southeast Missouri and western Tennessee until 11 p.m. CT, according to the Storm Prediction Center. The watch area includes Jonesboro, Arkansas; Paducah, Kentucky; and Memphis, Tennessee. Another watch is in effect for portions of southern and central Illinois, central and southwest Indiana and a very small portion of northwest Kentucky and southeast Missouri until 8 p.m. ET, according to the Storm Prediction Center. Many of the most intense thunderstorms are expected to strike after nightfall, heightening concerns. Tornadoes that occur at night are nearly twice as likely to be fatal as those during daylight hours, a 2022 study found. Some storms are expected to bring heavy rainfall, raising the risk of flash flooding across regions from the South to the Midwest. Storms will span most of the East Coast Monday The severe weather threat will spill into Monday as powerful thunderstorms continue to sweep eastward from the Appalachians to Louisiana and Mississippi during the morning hours. While some storms may briefly weaken with the morning light, they are expected to regain strength by the afternoon. By Monday evening, the severe weather threat will span nearly the entire East Coast, placing nearly 100 million people at risk. Cities from New Orleans to Boston fall within the affected zone, though the specific threats will vary. The storms are expected to linger overnight from the mid-Atlantic to the Northeast before moving into the Atlantic Ocean by Tuesday morning. A historic March for tornado activity This year has already seen an extraordinary number of tornadoes, with approximately 300 tornado reports logged since January, nearly double the 164 reported by this time last year. Since 2010, only three years — 2023, 2017 and 2013 —have recorded more tornadoes in the first three months of the year. Last year tornado activity surged in late spring and persisted through December, resulting in nearly 2,000 tornado reports. It was the second-most tornado reports in a single year on record, surpassed only by 2017. Residents across all affected regions are urged to stay informed and have multiple ways to receive weather alerts, especially in areas at risk for nighttime storms. The-CNN-Wire™ & © 2025 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved. About The Author