The turbid water rose high enough to begin filling second floors - a highly unusual sight for a city built on nearly flat terrain. Authorities urged people to get on top of their homes to avoid becoming trapped in attics and to wave sheets or towels to draw attention to their location.
Some people used inflatable beach toys, rubber rafts and even air mattresses to get through the water to safety. Others waded while carrying rubbish bags stuffed with their belongings and small animals in pet carriers.
As the floodwaters rose, the US National Weather Service offered another ominous forecast: Before the storm passes, some parts of Houston and just west of the city could receive as much as 1270mm of rain. That would be the highest amount ever recorded in Texas.
- Additional reporting: AP