Forecasters in the United States say the tropical storm Harvey may make a second strike on the already flooded city of Houston. The National Weather Service says the worst of floods were expected tomorrow and Thursday, although there is still uncertainty about the storm's path. <br/><br/>A record 75 centimetres of rain has already fallen on the city of Houston, turning roads into rivers. Catastrophic flooding in Texas is also expected to worsen in coming days as waters rise following the tropical storm. The Texas Gulf Coast is a key centre of the US oil and gas industry, and some of the largest refineries in the country have halted operations.<br/><br/>Texan officials say at least nine people are reported to have died in incidents related to the storm. More than 3,000 people have been rescued in and around Houston where about 6.6 million people live in the metropolitan area. Helicopters have plucked victims from rooftops. US President Donald Trump has promised swift action to help those affected. He is due to visit Texas today.