In Pictures: Heavy rain causes havoc in HoustonGetty ImagesHeavy rain in the aftermath of Hurricane Harvey has caused chest-high flooding in some parts of the city of Houston.Getty ImagesSome roads have turned to rivers along which the only way to rescue evacuees was by boat.ReutersMore than 25in (64cm) of rain has fallen in some parts of Houston, with a further 12 to 25in (30-64cm) expected over the next few days, the National Weather Service forecast.Getty ImagesSuch heavy rainfall in Houston is unprecedented, officials say, with recent rainfall equalling the average for an entire year.Getty ImagesOverwhelmed emergency services have cautioned residents to head for high ground or climb onto rooftops - but not into attics - so they can if necessary be picked up by rescue helicopters. More than 1,500 rescues have been carried out so far.ReutersHouston has opened numerous community centres for people forced out of their homes because of the bad weather but the mayor has urged people to remain in their homes and not call the emergency services unless they face life-threatening situations.ReutersInsurance experts have warned that flood damage across Texas from the bad weather may equal the trail of destruction left by Hurricane Katrina in 2005 - that was the most expensive natural disaster in US history.ReutersEmergency 911 operators in Houston received 56,000 calls over a 15-hour time period - seven times more than during a usual working day.ReutersThe centre of the storm is estimated at the moment to be about 125 miles away from Houston, but it is forecast to move closer to the city by Wednesday.Getty ImagesThe swift rise of the flood waters caught the authorities off guard, which is why Houston residents with boats are playing an increasingly important role in the rescue effort.EPAThe flooding had led to the closure of nearly every major road in Houston, with local media reporting that more than 170 roads are now waterlogged.Getty ImagesThe bad news for the people of Houston is that there is no sign of the rain easing up over the next few days.Houston flooding 'epic, catastrophic'Texas governor fears severe flooding riskUS storm to bring 'catastrophic' flooding