A tropical disturbance packing heavy rains in the Gulf of Mexico threatened the coast of Texas on Monday weeks after floods killed about 30 people in the state, the National Weather Service said.
Flash flood watches were in effect for central Texas and the Houston area, regions where flooding last month turned streets into rivers, submerged thousands of vehicles and surging water ripped houses off their foundations. Louisiana was bracing for flooding as well.
Outbound and inbound traffic in the Houston Ship Channel, the largest U.S. petrochemical port, was stopped on Monday to protect vessels from rough seas, officials said.
Captain Clint Winegar of the Houston Pilots Association said seas were several feet high. The U.S. Coast Guard urged boaters and beachgoers to stay out of the water.
Heavy rain hit parts of Texas over the weekend, pushing already high rivers closer to overflowing their banks.
In the Houston area, 10 inches (25.4 cm) or more of rain could fall by Thursday, and the M.D. Anderson Cancer Center, a world-renowned cancer treatment facility, said it was postponing surgeries.
Officials also imposed voluntary evacuations for some low-lying areas south of Houston.
The National Weather Service said the weather disturbance, which has a 90 percent chance of becoming a tropical depression or named storm, would lash the Gulf Coast with rain through Tuesday.
More than 45 percent of U.S. refining capacity is located along the U.S. Gulf Coast, which also is home to about half of total U.S. natural gas processing capability.
Chevron and Royal Dutch Shell have evacuated non-essential workers from oil platforms but have not shut production in a basin responsible for nearly a fifth of U.S. crude oil output.
Chevron is the No. 3 oil producer in the U.S. Gulf, and Shell is No. 1. Second-ranked BP Plc said it was monitoring the storm but operations continued as normal for now.
Other operators, including Hess, ExxonMobil, Murphy Oil, BHP Billiton and Williams Cos, said they were monitoring the weather, but hadn't evacuated any workers and production was unaffected.
Onshore, several major refiners with plants along the Texas Gulf Coast said they were preparing for the storm expected to reach shore Tuesday morning.
LyondellBasell said it was deploying sandbags at its refining and chemical facilities, and Shell said only workers essential to fuel production would work Tuesday.