AUSTIN, Texas—A sprawling blast of winter weather across the U.S. is likely to blame for the deaths of two people in Texas, where an unusually snowy emergency Monday knocked out power for more than four million people, shut down grocery stores and air travel and closed schools ahead of frigid days still to come. As nightfall threatened to plummet temperatures again into single digits, officials warned that homes still without power would likely not have heat until at least Tuesday, as frustration mounted and the state’s electric grid came under growing demand and criticism. “Things will likely get worse before they get better,” said Harris County Judge Lina Hidalgo, the top elected official in the county of nearly 5 million people around Houston. Law enforcement reported two men were found dead along Houston-area roadways. Causes of death were pending, but officials said the subfreezing temperatures were likely to blame. The …