By Jon Herskovitz
AUSTIN, Texas (Reuters) - Tropical Storm Bill was downgraded to a tropical depression on Wednesday as it moved across Texas, bringing heavy rains that flooded streets and snarled transportation in the state where severe weather killed about 30 people last month.
There were no reports of major damage or deaths from Bill, the second named tropical storm of the 2015 Atlantic hurricane season, which came ashore near the sportfishing town of Matagorda on Tuesday and then took a path into central Texas.
The storm is expected to bring sustained winds of near 35 mph (56 kph). Rainfall is expected to be 4 to 8 inches (10 to 20 cms) over eastern Texas and eastern Oklahoma and 3 to 6 inches over western Arkansas and southern Missouri. Some areas could see as much as 12 inches (30 cms), the National Hurricane Center said.
The heavy rains could cause rivers already swollen from torrential rains in late May to spill over their banks again.
"These rains may produce life-threatening flash floods," the weather service said.
About 120 flights were canceled at airports in Dallas and Houston, some of the nation's busiest, as of 7:45 a.m. CDT, tracking service FlightAware.com said. Houston had nearly a dozen road closures caused by high water.
The storm has prompted the National Weather Service to issue a flash flood watch for an area stretching from the Texas coast into Oklahoma, Arkansas, Missouri and Illinois, affecting more than 20 million people.
In Austin, Dallas and Houston, which were hit by floods in May, the owners of stores in low-lying areas deployed sandbags.
In Sealy, about 50 miles (80 kms) west of Houston, police had to rescue people caught in rising water as the floods cut power to numerous homes overnight.
"Please remain indoors and do not leave unless it is absolutely necessary," the Sealy Police Department said on its Facebook page.
Voluntary evacuations were called for some flood-prone areas south of Houston.
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.
Flooding could snarl work in onshore oilfields, but producers including EOG Resources and ConocoPhillips 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.
(Additional reporting by Terry Wade, Kristen Hays, Erwin Seba and Anna Driver in Houston; Editing by Bill Trott)