A busy stretch of severe thunderstorms is underway due to record heat and now the threats are ramping up, putting major metro areas from Chicago to Nashville under threat as the country hits the peak of tornado season.

Cities like Chicago, Minneapolis and Milwaukee are at risk for a severe weather outbreak on May 15, forecasters said.

The strong tornado threat Thursday includes Chicago, Milwaukee and a big chunk of central Wisconsin. Evansville, Indiana is at the heart of Friday’s tornado threat.