CHICAGO — Midwesterners got ready for the possibility of flooding Sunday as runoff from heavy rain and melting snowbanks bloated streams, and high wind caused new power outages for thousands in Michigan.

Flood warnings were posted Sunday over sections of Iowa, Missouri, Illinois, Indiana, Michigan and northwest Ohio, the National Weather Service said.

Following a week of heavy snow, ice and subzero temperatures, meteorologists said temperatures would rise into the 30s Sunday in the Chicago area, following Saturday’s high of 61. Farther east, New York City residents relaxed as temperatures headed for the mid- 60s Sunday.

In the Chicago suburb of Riverside, authorities encouraged residents along the Des Plaines River to evacuate Saturday night as water rose.