AS the remnants of Hurricane Isaac push their way up the Mississippi valley, spinning off severe thunderstorms and at least one tornado, some in Louisiana are impatient with the pace of restoring power.

While New Orleans streets were bustling again and workers were returning to offshore oil rigs, thousands of evacuees couldn’t return home to flooded low-lying areas of Louisiana and more than 400,000 sweltering electricity customers in the state remained without power.

The National Weather Service said a tornado touched down in an unpopulated area of north-central Illinois. There were no reports of damage. By midday on Saturday (local time), the storm had dumped up to 13 centimetres of rain in parts of Illinois.

The National Weather Service said it was bringing more rain and some drought relief to parts of the Mississippi and Ohio River Valleys.

In Louisiana, the number of people without power was down from more than 900,000. However, in heavily populated Jefferson Parish near New Orleans, parish president John Young complained about the pace of restoring electricity.

New Orleans Mayor Mitch Landrieu said he too was anxious to get power back on. “Like everybody else, my patience is wearing thin,” he said.

Parts of coastal Plaquemines Parish, where thousands were evacuated, remained under water. But in the water-logged town of Lafitte, Mayor Tim Kerner was allowing property owners and residents to return and begin cleaning up.

Gulf of Mexico oil platforms were being repopulated after Isaac forced a shutdown of most Gulf oil production.

People stuck inside stuffy, powerless homes were comparatively lucky. The governor’s office said more than 4,000 people were in state, local or Red Cross shelters as of Saturday morning and that doesn’t count others who took refuge with friends, family or in hotels.

LaPlace resident Roshonda Girrad was staying in a state-run shelter in Alexandria, 320 kilometres from her home. She was waiting for the chest-deep waters in her neighbourhood to recede.

“The showers are horrible. The food is horrible,” Girrad said. “I’m not from around here. I don’t know what’s going on. We’re in the dark.”

Isaac dumped as much as 40 centimetres of rain in some spots, and about 500 people had to be rescued.

In New Orleans, most of the downtown area and the French Quarter had power again on Saturday. The annual Southern Decadence festival, a celebration of gay culture, was under way. And the Superdome prepared to host a Saturday night college football game.

Newly nominated Republican presidential candidate Mitt Romney visited flood-ravaged communities on Friday, and President Barack Obama said he would arrive on Monday.

Crews intentionally breached a levee that was strained by Isaac’s floodwaters in southeast Louisiana’s Plaquemines Parish, which is outside the federal levee system. Parish President Billy Nungesser said the work was slow-going.