PEARL RIVER, La. — "I think what we're seeing right now is what we're going to get," J.J. Jennings, the police chief of this small and somewhat waterlogged city near the Mississippi border, said with nervous optimism.
What he was seeing at that moment Monday was a group of neighbors using pumps and sandbags to keep an ever-rising creek out of Ed Martensson's house, which was so hemmed in by water that a 12-year-old boy was fishing in the driveway.
After days of extraordinary rainfall — some places recorded more than 20 inches in less than 72 hours, the National Weather Service said — the rising waters that ruined homes are swelling the rivers, bayous and lakes of southern Louisiana.
"They've already got a lot of water down there, much like we have, and now we're sending more water down there," said Matt Hemingway, a Weather Service meteorologist in Shreveport, in northern Louisiana. "The entire state has been impacted."
Gov. John Bel Edwards has declared a statewide emergency, and President Barack Obama said Sunday that there were major disasters in seven parishes. Obama could soon extend federal assistance elsewhere in Louisiana, where thousands of people have evacuated and at least four deaths have been reported.
State officials said more than 6,100 structures had been damaged, with more expected.
In Mississippi, where a state of emergency was in effect and the National Guard was activated, the state's emergency management agency said at least 185 homes were destroyed, and hundreds more were damaged.
Gov. Phil Bryant said Monday there had not yet been enough destruction in Mississippi to seek a disaster declaration from Obama, but that the authorities were prepared for flooding and that the state might ultimately request federal aid.
Although Louisiana and Mississippi faced the gravest threats Monday, federal officials also issued flood warnings in more than a half-dozen other states.