Heavy rain, severe thunderstorms and the risk of tornadoes are threatening more than 40 million people from Michigan to Texas as a slow-moving cold front hovers over the region.

There’s a rare high risk for damaging winds and long-lasting powerful tornadoes to break out in a smaller area from southern Illinois to northeastern Arkansas Wednesday, including Memphis, the US Storm Prediction Center said. In addition, the severe thunderstorms will kick off days of heavy rain across the central US, said Frank Pereira, a senior branch forecaster at the US Weather Prediction Center.