Thousands of residents were fleeing Bangkok on Thursday as floodwater threatened to break through dikes protecting the Thai capital.
The government declared a five-day holiday from Thursday, and ordered residents of three northern districts to evacuate, as the Bangkok braces for potentially severe flooding over the weekend.
Read more on GlobalPost: Bangkok floods hit airport, close to city center
The BBC reported that Bangkok's bus and train stations were packed, and many roads jammed by crowds of people looking to get out.
It is understood that some northern districts are now 90 percent submerged.
The Guardian cited warnings that the city's main Chao Phraya river is likely to “overflow its defenses on Saturday, when high tides are expected to merge with the heavy run-off from further north”.
Bangkok governor Sukhumbhand Paribatra said:
"We're at a critical moment, we need to monitor the situation closely from 28 to 31 October, when many areas might be critical ... Massive water is coming."
More than 373 people have died since mid-July in Thailand's worst flooding or more than half a century.
Almost 2.5 million people, mostly in the north and central provinces, have been affected by the floods, which are partly the result of heavy monsoon rain.
Thai Prime Minister Yingluck Shinawatra said Bangkok, which has a population of 12 million, was “fighting against the forces of nature” and that authorities needed to let the water flow naturally out to sea.
"What we can do now is to manage it, so that it flows slowly, otherwise everybody will suffer."
According to Reuters, Thailand's defense ministry said 50,000 armed forces personnel were on hand with 1,000 boats and 1,000 trucks to help evacuate residents.