Thousands of evacuees could not return home in low-lying parts of Louisiana on Saturday and hundreds of thousands remained without power in the summer heat in Louisiana and Mississippi. There are also shortages of essentials, including food, water and ice.
Mandatory evacuations were held in Louisiana's St. Tammany Parish, south of the Pearl River diversion canal, after fears that Lock 2 would fail. The number of people affected by those evacuations was unknown.
The National Weather Service reported two tornadoes touched down in north-central Illinois and 5 inches of rain were dumped on other parts of the state. There were no reports of damage in the tornadoes.
Meanwhile, Republican presidential candidate Mitt Romney paid a visit to those affected by Isaac on Friday, President Obama plans to visit the region on Monday.
The Associated Press contributed to this report.