Hurricane Dolly slammed ashore and then loitered over deep south Texas as a tropical storm, dumping as much as a foot of rain in places and ripping roofs off buildings with 100 mph (160 kph) winds.
Emergency managers waited for Dolly to move on late into the night Wednesday and hoped to begin assessing the storm's damage Thursday even as they began to rescue people from flooded or damaged homes.
Dolly had weakened to a tropical storm by Wednesday night after hitting South Padre Island around midday as a Category 2 hurricane. But the storm drenched south Texas as it crept westward at an excruciating 7 mph (11 kph) into the evening. The National Weather Service expected Dolly to weaken to a tropical depression, turn to the northwest and accelerate slightly Thursday.
By 0900 GMT Thursday, the tropical storm was centered about 95 miles (150 kilometers) northwest of Brownsville with maximum sustained winds that had dropped to about 60 mph (97 kph).
Still, the danger had not passed as power lines hung across streets and water surrounded neighborhoods.
"Unless it's life or death," Tony Pena, Hidalgo County emergency management coordinator, urged residents to stay at home.
While the rain set records in Brownsville's Cameron County - ranging from six to 12 inches (15 to 30 centimeters) with another three to seven inches (eight to 18 centimeters) expected overnight - they did not appear to pose the threat to the Rio Grande's levees that had been feared.
The river rose steadily through the day in Brownsville, but did not reach flood stage.
"We're not experiencing any issues with the levees right now," Sally Spener, spokeswoman for the International Boundary and Water Commission, said late Wednesday. "The water is just not high enough."
But the torrential rains and fierce winds that lasted much of the day in south Texas still caught some by surprise.
By Wednesday afternoon, the community of Laureles north of Los Fresnos had been reduced to a chain of sunken islands, separated from the main roads by floodwaters of two feet or more in places.
Mailboxes barely peaked above murky, wind-swept waters where neighborhood loops met county roads.
Pedro Zuniga, his wife and their six children fled their mobile home for the comparative safety of a relative's wood-frame house next door. That home's owner had already left to take shelter in another relative's brick house.
Peering out the back door at the trailer he deemed to wobbly for his family, Zuniga said the water crossing his yard toward a canal behind was not as high as he had seen it a few years ago when it reached the base of his elevated trailer.
"We were going to go to a shelter, but they said there was only one so we decided to stay," said Zuniga's wife, Aleida Cardenas, 29. "But we didn't know it would be this bad."
But others did head to shelters. More than 5,000 people moved to public shelters in the three hardest-hit counties and the numbers were expected to grow Thursday as more people became stranded by floodwaters.
In Hidalgo County, Pena said there were several incidents late Wednesday requiring emergency personnel to rescue people from homes.
One family was left huddling in their topless house after winds blew the roof off in the northeast part of the county until rescuers arrived, Pena said. In Cameron County, sheriff's deputies rescued a family of eight from Los Fresnos after floodwaters surrounded their home.
The only serious injury reported Wednesday occurred when the wind knocked a 17-year-old boy from a seventh-story balcony on South Padre Island. The boy suffered a broken hip, leg and a head injury but could not be transported off the island until about 5 p.m. (2200 GMT) The causeway linking the island to the mainland reopened to the public at 8:30 p.m. (0130 GMT Thursday), said Melissa Zamora, an emergency management spokeswoman on the island.
The island sustained some of the storm's heaviest damage and was still without power Wednesday night. Roofs were torn off hotels and homes, there was significant flooding that had begun to subside and debris was everywhere. A curfew was imposed for 8 p.m. (0100 GMT Thursday), Zamora said.
No deaths were immediately reported in Mexico, but Tamaulipas state Gov. Eugenio Hernandez said 50 neighborhoods were still in danger from flooding. About 13,000 people had taken refuge in 21 shelters, he said.
"Strong winds are no longer the problem. Now we have to worry about intense rain in the next 24 hours," Hernandez said.
Earlier in the day, Mexican soldiers made a last-minute attempt to rescue people at the mouth of the Rio Grande, using an inflatable raft to retrieve at least one family trapped in their home. Many people farther inland refused to go to government shelters.
Many Texans heading north were stopped at inland Border Patrol checkpoints, where agents opened extra lanes to ease traffic flow while still checking documentation and arresting illegal immigrants, said sector spokesman Dan Doty. At one checkpoint on U.S. 77, smugglers were caught with nearly10,000 pounds (4,540 kilograms) of marijuana.
The U.S. Census Bureau said that based on Dolly's projected path, about 1.5 million Texans could feel the storm's effects. Texas Gov. Rick Perry declared 14 south Texas counties disaster areas and sought federal disaster declarations.
Perry was scheduled to fly over the region Thursday.
The last hurricane to hit the U.S. was the fast-forming Humberto, which came ashore in south Texas last September.
The busiest part of the Atlantic hurricane season is usually in August and September. So far this year, there have been four named storms, two of which became hurricanes. Federal forecasters predict a total of 12 to 16 named storms and six to nine hurricanes this season.