(Bloomberg) -- Harvey may no longer be a major hurricane, but the trouble for Texas is just beginning with forecasts for unprecedented flooding across the heart of U.S. energy production and in Houston, the nation’s fourth-largest city. Harvey was the strongest storm to hit the U.S. since 2004 when it struck near Rockport as a Category 4 hurricane. The storm system is flooding a region that has a cluster of refineries that process 5 million barrels of oil a day. About 1 million barrels a day of crude and condensate refining capacity in the state have been shut by companies including Valero Energy Corp., according to company statements, government releases and people familiar with the situation. Its path through the Gulf shuttered 24 percent of oil production, along with the port of Corpus Christi, which ships the largest amount of U.S. crude overseas.