By Kristen Hays and Terry Wade
HOUSTON (Reuters) - Tropical Storm Bill headed further into central Texas with heavy rains and high winds on Wednesday before losing its punch and no serious injuries were reported, relieving officials and residents just three weeks after floods killed about 30 people in the state.
The National Hurricane Center said the storm had weakened into a tropical depression.
The second named tropical storm of the 2015 Atlantic hurricane season made landfall on Tuesday near the sportfishing town of Matagorda, then lost much of its power, the U.S. National Weather Service said.
There were no reports of substantial damage, and oilfields in the Gulf of Mexico and near the coast were not impacted by the storm. Refineries and a nuclear power plant, the South Texas Nuclear Generating Station in Bay City, also operated normally.
But about 300 flights were canceled at the two airports serving Houston, the fourth-largest U.S. city, according to tracking service FlightAware.com. Vessel traffic was also halted in the Houston Ship Channel, the waterway to the biggest U.S. petrochemical port, and the ports of Galveston and Texas City.
"This is a rain event," Houston Mayor Annise Parker said at a news conference. "This is a normal rain event."
Despite the weakening storm system, forecasters said tornadoes were possible across much of Texas.
Flash flood watches were issued for six states. The watch area included Houston and central Texas, where floods over Memorial Day weekend last month swept away thousands of vehicles and damaged homes.
The storm was forecast to sweep over the Texas capital of Austin and then drive on to Dallas on Wednesday.
Heavy rain had already drenched parts of Texas over the weekend, pushing high rivers closer to overflowing their banks.
The National Hurricane Center said the storm could bring up to 8 inches (20 cm) of rain to eastern Texas and Oklahoma and up to 4 inches (10 cm) to Arkansas and southern Missouri.
Voluntary evacuations were called for some low-lying areas south of Houston.
Flooding could snarl work in onshore oilfields, but producers including EOG Resources (NYSE:EOG) and ConocoPhillips (NYSE:COP) said they were unaffected.
More than 45 percent of U.S. refining capacity and half of natural gas processing capacity sits along the U.S. Gulf Coast.