The US Midwest is braced for more bad weather after a weekend of storms that left eight people dead and forced hundreds from their homes.
Meanwhile, the US east coast is suffering a heatwave, with temperatures forecast to hit 100F (38C).
Flood warnings remain in place for parts of Indiana, where rescuers have been using boats and helicopters to reach those stranded by rising waters.
More bad storms may hit Indiana, Kansas and Oklahoma on Monday.
State of emergency
President George W Bush declared a major disaster in 29 counties in Indiana late on Sunday, freeing up resources for aid efforts.
"This thing came on fast with such a radical deluge of water that people were describing going from a feeling of security to waist-deep water in a matter of 15 or 20 minutes," said Indiana Governor Mitch Daniels.
Thunderstorms dumped heavy rain on Indiana and other Midwest states
A nursing home and a hospital have been evacuated, as well as hundreds of homes.
Meanwhile, Wisconsin Governor Jim Doyle sought emergency aid for 29 of the counties in his state, and a state of emergency has been declared in nearly a third of Iowa's 99 counties.
In Michigan, two delivery workers drowned when their vehicle became submerged in a creek swollen by heavy rains.
A tornado touched down in Omaha, Nebraska, causing damage to dozens of homes but no major injuries.
Hundreds of thousands of homes and businesses across the region were left without electricity after storms took down power lines.
In Chicago, Illinois, residents are continuing to clear up after damage caused by high winds over the weekend.
The National Weather Service has issued heat warnings for eastern states including Connecticut, New York, New Jersey, Virginia and North Carolina, as well as the nation's capital, Washington DC.
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