Thunderstorms have killed four people and knocked out power to nearly a million homes and businesses in south-east Texas.”We have a storm with 100 mph winds, the equivalent of Hurricane Ike, considerable damage downtown,” said the mayor of Houston, John Whitmire.Two deaths came from fallen trees and one from a crane blown over.The storm has now moved on to neighbouring Louisiana with flood warnings in place for the Gulf Coast.In Houston, traffic lights were out, office windows blown through and glass strewn across the city’s streets.Video footage from downtown shows windows and part of the…