(CNN) -- Tropical Storm Alex strengthened in the Gulf of Mexico Tuesday night to become the first June hurricane on the Atlantic side of the United States since 1995, the National Hurricane Center said.
Alex gained strength and upgraded to a Category 1 hurricane Tuesday night, the hurricane center said.
The hurricane center's advisory issued at 11 p.m. ET said Alex was moving to the west at 9 mph and was expected to hit the northern Mexico coast Wednesday evening. The center reported the storm had maximum sustained winds of 75 mph.
President Barack Obama issued a federal emergency declaration for Texas ahead of the expected arrival of Alex, the White House said Tuesday night.
The hurricane center's maps tracked the storm churning off the northwestern coast of Mexico's Yucatan Peninsula in the Bay of Campeche early Tuesday. It was moving at 12 mph to the north-northwest, the Hurricane Center said at 8 a.m. At 5 a.m., the storm had been reported moving at 8 mph.
A hurricane warning was issued for the Gulf Coast from Baffin Bay, Texas, to La Cruz, Mexico. A hurricane warning means that hurricane conditions and tropical storm-force winds are expected in the forecast area within 36 hours.
A tropical storm warning was in place along the Texas coast from Baffin Bay to Port O'Connor.
The storm continued to move away from the massive BP oil catastrophe near the Louisiana coast in the northern Gulf of Mexico, but it already was complicating cleanup efforts. The storm created 12-foot waves on Tuesday and oil skimming ships were sent back to shore, from Louisiana to the Florida Panhandle.
The rough seas may force crews to replace and reorganize booms meant to deter the oil from reaching shore, reported CNN's Ed Lavandera.
Florida Gov. Charlie Crist said that even though Florida may dodge a bullet with this storm, the Atlantic hurricane season is just beginning.
"In Florida, we've had a lot of hurricanes a number of years ago, but we handled them very well," he told CNN's Campbell Brown. "The difference and the distinction that we face now is that we have a Gulf of Mexico that's full of oil. So our hope and our prayer is that we don't have a mixture of hurricanes with oil that could potentially damage the beautiful beaches of Florida. But if we do, we're prepared for it."
Brownsville, Texas, Mayor Pat Ahumada said his city was expecting to distribute 60,000 sandbags and provide shelter for roughly 2,000 families. Utility crews were put on standby to handle outages. At the same time, 90 buses had been provided by the state government in case an evacuation is required.
"I expect about 10 percent of residents to evacuate voluntarily, which already started yesterday," Ahumada said. "I see a steady flow of people going out, but no bottlenecks -- which is good."
"We're not taking it lightly," he said. "We're ready for a worst-case scenario."
On Monday, Texas Gov. Rick Perry issued a disaster proclamation for 19 counties and ordered the pre-deployment of state resources. The governor's declaration allows the state to initiate necessary preparedness efforts, such as pre-deploying resources to ensure local communities are ready to respond to disasters.
The governor's order puts up to 2,500 National Guard personnel, eight UH-60 helicopters and three C-130 aircraft on standby for rapid deployment as needed, Perry's office said in a statement.