Slidell , Louisiana ( CNN ) -- Authorities dropped a mandatory evacuation order Sunday for neighborhoods threatened by a strained lock on a southeast Louisiana canal , but still recommended people stay away . `` As there is still a potential threat , even though reduced , a voluntary evacuation remains in place until the Army Corps of Engineers deems the lock stable and safe , '' the president and sheriff of St. Tammany Parish announced late Sunday morning . `` Please stay vigilant . '' The lock authorities feared would fail was on a man-made canal that juts off the Pearl River , near the Mississippi state line . The river has been swollen by rain from last week 's Hurricane Isaac , forcing authorities to relieve pressure on the structure by releasing water Saturday and Sunday . Earlier Sunday , St. Tammany Parish President Pat Brister told CNN the water level at the lock has been reduced `` tremendously '' since Saturday night , and `` We feel a lot better . '' But the waters were still rising Sunday afternoon . Christina Garcia stopped by a boat ramp around the corner from her home periodically , counting off heel-to-toe steps from the waterline to the top to track the river 's rise . `` When I first started , it was like , 14 , and now I 'm down to probably 10 , '' Garcia said . The river `` is starting to come up slowly , but there is some concern . We are trying to take all precautions . '' Forecasters predict the Pearl River will crest Monday at 19.5 feet , more than five feet above flood stage . That will result in `` major flooding '' of at least two subdivisions near the banks and threaten areas in the southeastern corner of the parish , according to the National Weather Service . U.S . Homeland Security Secretary Janet Napolitano visited the parish on Sunday , during a trip that also included stops in Mississippi where she met with that state 's governor and other officials . President Barack Obama will be in Louisiana on Monday for a briefing with local officials and to tour flood-damaged areas in St. John the Baptist parish . What 's left of Isaac , meanwhile , soaked in and around the Ohio River valley on Sunday , bringing stormy weather from Nashville , Tennessee , to Indianapolis . The storm 's remnants have brought much-needed rain to parts of the lower Midwest . But the system skirted most of the Midwestern and Plains states where this year 's drought -- which the National Climatic Data Center reported last month was affecting a majority of the U.S. mainland , the most since 1956 -- has been most devastating . `` Certainly , it helped some locations in our far eastern counties in Oklahoma , but there was very little beneficial rain , '' said Pete Snyder , a National Weather Service meteorologist in Tulsa . Nearly all of Oklahoma , Arkansas , Missouri , Iowa , Nebraska and Kansas fall under the worst two drought categories . Isaac dumped heavy rain across southern Arkansas last week , with some flooding reported around Little Rock and Pine Bluff . But the northwestern city of Fayetteville , which is nearly 11 inches below its normal rainfall totals for the year , got just over an inch , Snyder said . Flood warnings remained posted for parts of two northeastern Arkansas counties along the Cache River on Sunday . Parts of Missouri and Illinois saw up to six inches of rain Saturday , and the National Weather Service issued a flood warning Sunday for parts of southern Illinois . Isaac is blamed for at least 19 deaths in Haiti and at least four more in Louisiana and Mississippi after making landfall last week as a Category 1 hurricane -- on the seventh anniversary of Hurricane Katrina -- near the mouth of the Mississippi River . The storm posed the first real test to New Orleans following a $ 14.5 billion federal effort to reconstruct the city 's flood control system after it failed during Katrina in 2005 . Katrina killed nearly 1,800 people , most when the storm overwhelmed the levee system and flooded the city . Though much weaker than Katrina when it came ashore , Isaac moved slowly and dumped enormous amounts of rain on Louisiana and Missouri . In Plaquemines Parish , near the mouth of the Mississippi River , homes and businesses flooded after a parish-maintained back levee failed . Officials were intentionally breaching levees in strategic areas in the parish , in hopes of getting `` the bulk of this water out in five to seven days , '' Plaquemines Parish President Billy Nungesser said Saturday . Hundreds of thousands in the region were without power early Sunday , including at least 320,000 Entergy Louisiana customers , officials said . Residents began returning home over the weekend in Helena , Mississippi , where National Guard troops rescued hundreds trapped by rising waters brought on by Isaac . Annie Judge returned home Saturday to find more than four feet of water inside her home . `` Clothes , my laptop , a bunch of baby stuff , pictures , '' all ruined , she told CNN affiliate WLOX . `` All the furniture is ruined . '' CNN 's Greg Botelho , Chelsea J. Carter , Matt Smith and David Ariosto contributed to this report .
NEW : Secretary Napolitano visits the Gulf Coast ; President Obama is coming Monday . A mandatory evacuation is lifted around a strained Louisiana canal . The rain-swollen Pearl River threatens to flood Louisiana homes . Hurricane Isaac dumped heavy rains on the area last week .