Flash floods put towns underwater and forced evacuations in Minnesota and Wisconsin. A strong system caused the heavy rain and flash flooding in the Upper Midwest. Flood Reports Flash floods put towns underwater and forced evacuations in Minnesota and Wisconsin. A strong system caused the heavy rain and flash flooding in the Upper Midwest. Some of the worse flooding came a week after the flood. Near record stage on the Minnesota river in New Ulm, Mankato, St Peter, Jordan, Shakopee, Savage, and breaking records in Henderson. Records were also broken on the Cannon River and the Zumbro River.