The blackout kept air conditioners from running as temperatures soared into triple digits. Four deaths in the region had been blamed on the storms or the heat.
As of Monday morning, about 231,000 homes customers were still without power, according to Ameren Corp. That was down from the more than a half-million homes and businesses that lost power when the storms struck last week. Some 4,000 utility workers from as far away as Arizona have been working around the clock to restore service.
Ameren vice president Richard Mark said Monday that 90 percent of those without power could have the lights back on by Tuesday, with the rest expected to be back up by Wednesday.
CBS News correspondent Kelly Cobiella reports it is the worst power failure in this city's history. Last week's one-two weather punch - storms Wednesday and Friday - knocked out power to half a million customers during a heat wave.
For the hundreds of thousands of people waiting on repairs, food has gone bad and frustration is rising.
What have the past five days without power been like for a resident?
"Miserable. Just miserable," Learon Aaron said. "You can't find no ice, you can't find water, you know, everything is hard to find."
Emergency rooms have been inundated with patients who rely on electricity for oxygen and other medical needs. The Missouri Health Department called on the help of all registered nurses and nursing assistants in the area and a team of nurses arrived Saturday from Kansas City to work in St. Louis hospitals.
Blackouts also affected parts of California, where utilities worked to restore electricity to thousands of customers Monday as a severe heat wave taxed power plants and threatened to push the state into a power emergency with the potential for more blackouts.
In New York City, 3,000 to 4,000 customers of Con Edison entered their Monday in part of the borough of Queens. That blackout started in the middle of last week's heat wave on a day the temperature was near 100 degrees.
In St. Louis, some 100 dump trucks rolled through city streets Sunday collecting branches and entire trees smashed by the storms. The Missouri Army National Guard was helping with the cleanup.
"It's hard to believe your eyes when you are looking at something this massive," said St. Louis Parks Director Gary Bass. What isn't turned chopped into mulch for landscaping will be cut into free firewood or hauled away, he said.
President Bush on Friday approved Missouri's request for an expedited disaster declaration, which mobilizes the Federal Emergency Management Agency and provides federal funding for debris removal and other emergency needs.