(CNN) -- As water levels already at or above flood stage continue rising in rivers in southwestern Louisiana, the weather forecast says more rain is on the way.
But it won't be as bad as the torrents that have caused widespread flooding in seven parishes, the National Weather Service predicts. There is about a 20% to 50% chance of showers and thunderstorms in much of the region through Monday.
Gov. Bobby Jindal declared a state of emergency Thursday afternoon after thunderstorms drenched the state with as much as a foot of rain this week. Hundreds of people have been evacuated. There were no initial reports of injuries.
Many rivers in the southwest, closer to Texas, where flooding has been prominent, are still rising and expected to crest over the weekend. At least one is predicted to hit major flood stage.
The flood region is a low-lying prairie, and water about thigh-deep spread over a broad region, inundating homes and cars.
The town of Eunice has had 12.25 inches of rain since Tuesday, a hydrologist with the National Weather Service said.
St. Landry Parish spokeswoman Megan Vizena said 30% of the area was underwater.
Authorities in Franklin, near the Gulf of Mexico, evacuated 118 people after 7 inches of rain washed over some roads and bridges, the weather service said on its website.
In Acadia Parish, rescuers saved close to 80 people from rising water, including 20 at an oil well.
The National Weather Service said at least two EF-1 tornadoes struck Thursday, one of which damaged 50 homes in St. Martin Parish. A third tornado was sighted in Iberville Parish, according to CNN affiliate WBRZ.
Rivers to Louisiana's southeast, near Mississippi, have also gone over flood stage, but inundation has not been dramatic there. Much of the region is hilly and not as prone to flooding. Those rivers have also already crested, according to NWS data.
The heavy rainfall accompanies a broad warming trend covering the southeastern United States and reaching into the Midwest, according to the weather service. Both have the same root cause, said CNN meteorologist Pedram Javaheri.
"It's a southerly flow coming over the Gulf of Mexico," he said. "It's a subtropical air mass," Pedram Javaheri, and can spark thunderstorms as it collides with a cooler front coming over from Texas.
2012 was the warmest year on record for the contiguous 48 states of the United States, according to the National Weather Service. But Javaheri sees no connection between that and the current weather system.
Cold weather should return soon, giving the country a normal start into 2013, he said. Four-fifths of the country will see colder than average temperatures in the third week of January.
CNN's Steve Almasy, Sean Morris and Joe Sutton contributed to this report.