The record rainfall of 440 mm in 12 hours brought the capital to a virtual standstill and displaced around 60,000 persons.
The parliament house remained inaccessible to normal vehicles and naval boats and armoured vehicles were used to take the house speaker and MPs to attend the meeting in a submerged parliamentary complex built in the middle of an island in a man-made lake.
The water-logged parliament complex had to restrict its session to eight minutes.
With the power supply disrupted and ground floor under three-feet high water, electric torches were used to lead the parliamentarians inside.During the brief session held in darkness, the parliament approved Rs 15 billion to expedite development projects in the country.
"Entrance area and the ground floor of the parliament were under three feet high water this morning and the power supply to the building was also disrupted," parliament officials said.
"Personal security officials had to use electric torches to lead the parliamentarians in to the chamber".
"The midnight shower displaced around 60,000 persons, majority of them in the western province" Disaster management Minister A H M Fowizi said.He said Rs 15 million has been allocated for relief operations.The unusually heavy rains forced schools to close and semester exams were postponed, educations officials said.
Heavy traffic was seen on almost all roads leading to Colombo as they were flooded and disruption of power supply paralysed the traffic lights system.
Nearly 2,000 soldiers from all three forces have been deployed to assist the people affected by the floods, military officials said.
"The navy had to deploy boats to rescue people stranded and distribute essential items," a navy spokesman said.
The highest rainfall in 18 years recorded 440 mm in Colombo early this morning.
Many other parts of the island were also affected, Meteorological department said.