Texas and Mexico batten down the hatches as tropical storm Dolly builds into a hurricane

Hurricane warnings were issued late Monday for parts of the Texas and Mexico coasts, meaning hurricane conditions were expected in those areas by the end of Tuesday.

Dolly was expected to make landfall later this week and bring with it high winds and up to 20 inches of rain in coastal areas. 

Weather threat: A satellite image showing tropical storm Dolly as it enters the Gulf of Mexico

Emergency officials feared major flooding problems and urged coastal residents to prepare. Gov. Rick Perry activated 1,200 National Guard troops and other emergency crews.

Even as far up the coast as the Houston area, Harris County officials told residents to be ready in case the storm changes course and heads their way.

The U.S. National Hurricane Center in Miami issued a hurricane warning from Brownsville north to Port O'Connor.

Meanwhile, a tropical storm warning was issued from Port O'Connor to the San Luis Pass, a strait south of Galveston.

Mexico also announced a hurricane warning from Rio San Fernando north to the U.S. border.

A tropical storm warning and a hurricane watch were also in effect from La Pesca to Rio San Fernando.

Big surf: Waves break at the beach in the resort city of Cancun, Mexico, a few hours before the arrival of tropical storm Dolly

Just the beginning: Strong waves batter levees at hotels zone in Cancun

Forecasters said Dolly was expected to make landfall late Tuesday or early Wednesday as a Category 1 hurricane, which has with sustained winds of 74-95 mph.

Texas officials said they wouldn't order evacuations along the coast unless Dolly strengthens to a Category 3, with sustained winds of at least 111 mph.

The center of Tropical Storm Dolly was located about 295 miles southeast of Brownsville this morning and it was moving west at about 15 mph. Tropical storm-force winds extended outward up to 160 miles.

There are about 2 million people in the Rio Grande Valley, which includes popular summer beach resort South Padre Island.

Officials readied to evacuate residents in flood-prone areas and urged recreational owners on South Padre to head for higher ground.

"That amount of rain will present a big flooding problem for us," Cameron County Emergency Management Coordinator Johnny Cavazos said.

Storm precautions: A resident boards up his home in Corpus Christi, Texas this morning

Mindful of the disastrous evacuation before Hurricane Rita hit the Texas Gulf Coast in 2005 - when far more people died from heat-related injuries and auto accidents fleeing the storm than from the severe weather - Gov. Perry also ordered 250 buses to be staged in San Antonio.

He also ordered fuel teams to be ready to keep gas stations supplied and to help stranded motorists.

In the Houston area on Monday, Harris County Judge Ed Emmett asked residents of the state's most populous county to keep their gas tanks full, stock up on supplies and make sure they have plans ready to either evacuate or ride out a storm.

At a Home Depot in Brownsville near the border between the two countries, residents bought plywood, generators, batteries and flashlights, said store operations manager John Paul Martinez. He said a lot of people were just learning of Dolly, which became a tropical storm Sunday.

Shell Oil said it was evacuating workers from oil rigs in the western Gulf Of Mexico, and the federal government was trying to decide whether they could begin construction on a new border fence, which was to be combined with levee improvements along the Rio Grande in Hidalgo County.