BANGKOK — Severe flooding in southern Thailand has caused at least 33 deaths since the weekend, officials said, as dramatic video footage showed people whose homes were virtually engulfed by water awaiting help on rooftops.

About 1 million households and more than 2.7 million people have been impacted by floods in 12 southern provinces triggered by heavy rains, the Department of Disaster Prevention and Mitigation said Wednesday.

The accumulated rainfall began to decrease Wednesday and authorities were hopeful water levels would start to recede, but the Meteorological Department issued a warning for heavy rains and flash flooding in the country's southern region through Wednesday.

Prime Minister Anutin Charnvirakul on Tuesday declared a state of emergency for Songkhla province, which includes southern Thailand’s biggest city, Hat Yai, citing the “unprecedented severity” of the flooding that has caused widespread damage.

Streets in Hat Yai were impassable and low-rise buildings and cars nearly submerged by rising water, trapping thousands of people. Some residents on higher floors were given food baskets, hoisted up from rescue teams in flat-bottom boats.

Footage from a camera drone broadcast by Thai PBS showed a family of five in Hat Yai being rescued Tuesday from the rooftop of their house, which was nearly submerged. The family, including an older woman, appeared in the video as colorful specks in a landscape of flat, brown water. They had smashed through the large, grey roof and were spotted by emergency workers, who loaded them onto a lifeboat at the edge of the slanted roof.

The situation at Hat Yai Hospital is especially critical, Public Health Minister Pattana Promphat said Wednesday, explaining that the facility's electricity could be cut off because of the high water. About 50 patients requiring intubation were airlifted out by army helicopters to other hospitals and some 600 other patients are likely to be evacuated along with hospital personnel, he said.

The Public Health Ministry said it would deploy a mental health team to assist medical personnel and members of the public dealing with stress.

The Thai navy’s sole aircraft carrier, the HTMS Chakri Naruebet, sailed from its berth in eastern Thailand to serve as an offshore command center for relief operations. The air force base at Bangkok's Don Mueang airport will serve as a staging area for flying relief supplies to affected areas, the government said.