The eye of the Category 3 storm came ashore before dawn near San Fernando, about 75 miles south of the U.S.-Mexico border. Forecasters predicted the storm could dump up to 15 inches of rain as it moves inland, causing flash floods and landslides.
Texas was not in the direct path of the storm, but Emily's outer bands began lashing the state's southern tip Tuesday and meteorologists said 2-4 inches of rain could fall over the lower Rio Grande Valley. The National Hurricane Center said isolated tornadoes also were possible in the south.
On Tuesday, army trucks roamed the streets of small Mexican fishing villages, collecting evacuees laden with suitcases and rolled-up blankets.
Officials in Tamaulipas state, which borders Texas, said 18,000 people had been evacuated from 20 low-lying, seaside communities, including nearly everyone from Carbonera, a fishing hamlet.
In San Fernando, a community of 60,000 farther inland, life came to a standstill before dusk Tuesday. Relentless rain left large puddles in the streets, and most storefronts were covered with plywood.
In southern Texas, campers emptied beachfront parks on South Padre Island and hundreds of other tourists left. Residents piled up sandbags to hold back possible floodwaters and boarded up windows of businesses and homes, while officials converted schools into shelters.
At Elma E. Barrera Elementary School, one of several shelters in Texas' Cameron County, families staked claim to areas around the edge of the gym floor with mattresses, blankets, coolers and televisions. Pajama-clad children played basketball or video games.
Cindy Ruiz, 32, sought shelter at the school with 12 other relatives, including her husband and eight children. The children worked on puzzle books while the adults monitored weather reports.
"This is our first hurricane," said Ruiz, who moved with her family to Texas from Iowa a few months ago. "We didn't want to take any chances with that many kids at home."
In La Pesca, Mexico, residents were taken to a naval base on a relatively high point on the edge of town. There, excited children raced giddily about, shrieking and laughing as their parents settled in.
"Now that there is help, we must accept it," said Marta Neri, a 30-year-old who arrived with her three small children.
In another part of town, 67-year-old fisherman Felipe Portillo helped his sons haul five fiberglass fishing boats off the beach and up to the roadside, away from the water.
"Overconfidence kills men," Portillo said. "Running is your best defense."
It was Mexico's second hit in a week from Emily. The storm slammed into the Yucatan Peninsula early Monday with winds of 135 mph, ripping the roofs off resort hotels and stranding thousands of tourists along the famous Mayan Riviera, which includes the resort of Cancun.
It lost strength as it swept over land, but regained momentum as it crossed the Gulf of Mexico and headed back toward the northeastern coast.
No one was killed and no major injuries were reported, according to federal officials surveying ongoing cleanup efforts.
Mexico and U.S. oil companies evacuated workers from offshore installations in the northern Gulf of Mexico. Some 16,000 workers were told to return to Mexican installations in the southern Gulf on Wednesday.