CHICAGO -- More heavy storms were headed to the flood-ravaged US midwest Monday as the east coast wilted in a sweltering heat wave, the National Weather Service warned.

Local media reported at least eight people were killed in the weekend storms which flooded scores of homes and roadways and left hundreds of thousands without power.

"There are some counties in which every road is closed or under water," said Pat Slattery, a weather service spokesman.

Several tornadoes caused considerable damage as they cut a swath through a nine-state area from Texas to Southern Minnesota on Saturday and Sunday and some areas saw as much as 25 centimeters (10 inches) of rain, he said.

"Today our concern has turned to flooding and flash flooding in much of that area," he told AFP.

"Any rain that falls anywhere in this area is going to be coming down on saturated soil and there isn't anywhere for it to go."

A number of bridges have been closed because of the heavy rains and a pedestrian suspension bridge in Charles County, Iowa collapsed, he said.

Some 20,000 people in Mason County, Iowa are without clean water after the water treatment plant was flooded and a number of mobile homes were washed away by floodwaters.

The governor of Indiana has called in the National Guard to help build temporary levies and clean up the damage after declaring a state of emergency in 23 counties over the weekend, just a week after some 41 counties were declared a disaster because of tornadoes and heavy rains.

The flood waters came up fast and hit areas previously considered safe from nearby rivers and streams.

"I looked out my back window and saw water coming up farther," Ann Lobsiger told CNN as she stood by a pile of her soaked belongings outside her home, which got about 90 centimeters (three feet) of water.

"It had never come up in my yard before. And a few minutes later my neighbor banged on the door and said, 'look.' The street was literally a river."

Lobsiger called her husband and told him to rush home. By the time he got there, the water was so high he had to back their truck up to the front door to salvage what they could.

"We had maybe four minutes. We just rapidly threw in pictures, and family videos. And an antique rocking chair that was my great-grandmother's."

State officials said they were working to protect areas downstream from the flooding as rivers crested, and were using boats to evacuate people stranded by flooded roadways.

"We are looking for it to get worse before it gets better. Plus we are looking at some more rain today," John Erickson, a spokesman for the Indiana department of homeland security told AFP.

"We've had one confirmed death. But the scope of the emergency has been so immense we feel that we have been really lucky" that there weren't more dead, he said.

Some 3,000 people took shelter from the heat in 40 cooling centers set up by the city of New York while about 600,000 more New Yorkers headed to the beaches, television station NY1 reported.

About a thousand people were without power in the city as officials warned residents to conserve power by turning off air conditioning units and closing the blinds when they're not at home in order to prevent wider blackouts.

Meteorologists predicted New York could beat a record set in 1933 of 98 degrees Fahrenheit (36.7 Celsius) after temperatures hit 97 degrees before lunchtime.

The heat index, which takes into account the impact of humidity, could hit 107 degrees (41.7 Celsius) in the afternoon.

This is the first heat wave -- three consecutive days of temperatures over 90 degrees Fahrenheit (32.2 Celsius) -- experienced on the east coast since August 2006, the national weather service said.