Rescuers in Colorado say they won't make special trips back into isolated, flood-ravaged areas for people who decide to stay and then change their minds.
Anyone who does stay faces weeks without electricity, running water and basic supplies. Forecasters say they expect more rain to fall.
Rescue work continues with thousands of stranded residents eager to escape the Rocky Mountain foothills.
Gov. John Hickenlooper took a helicopter tour of the flooded areas yesterday and President Barack Obama signed a disaster declaration.
The surge of water has now reached the plains east of the mountains, cutting off even more communities.
Hundreds of people still haven't been heard from in the flood zone, which has expanded to cover portions of an area nearly the size of Connecticut.
A woman is missing and presumed dead after witnesses saw floodwaters destroy her home. Four people have been confirmed dead since Wednesday, but authorities say that number is likely to grow.
So far, the National Guard says more than 1,200 people have been evacuated over two days.
Massive flooding in New Mexico has killed at least one person and prompted an emergency declaration from Gov. Susana Martinez.
Floods caused by heavy rains broke through dams and inundated neighborhoods yesterday.