Severe monsoon rains have battered the north and west of the country, displacing up to 110,000 people, many in remote towns and villages, according to aid agency reports.
Some areas in the country have become engulfed by heavy rains since mid-July, destroying farmland, roads, railway lines, bridges and houses.
Roads from central to northern Myanmar – which are crucial to the rescue effort – have been especially badly affected, according to a UN Office for the Coordination of Humanitarian Affairs (OCHA) report.
"I've never experienced such a terrible flood in my life," Thein Tun, a 57-year-old retired teacher, told Reuters by telephone from Mrauk-U in western Rakhine state, one of the worst-hit areas yet to receive aid.
"The entire town has been under water for a few days."
The UN said the military in Myanmar – which is also known as Burma – was working together with local aid groups to carry out rescue and relief operations.
Authorities in the country have urged those who are capable of travelling to move to safer areas because a cyclone forming in the Bay of Bengal could potentially bring more heavy downpours and strong winds, according to the Global New Light Of Myanmar newspaper.
Flights to the city of Sittwe in the western state of Rakhine have been cancelled.
It is home to around 140,000 displaced people, mainly Rohingya Muslims, who live in makeshift camps close to the coast, according to Reuters.
"Local authorities, the Union Government, the military, as well as the Myanmar Red Cross Society and local civil society organizations are responding to the situation, carrying out rescue operations and providing food, water, blankets, medical and other basic necessities to those affected," the UN's Office for the Coordination of Humanitarian Affairs said in a statement Thursday.
State newspapers reported on Friday that former military commander and president Thein Sein had called on Cabinet ministers to go out into the field to supervise flood-relief operations.
On Thursday, actress and UN special envoy Angelina Jolie Pitt visited Myitkyina township where thousands of people live in make-shift accommodation after being displaced after a ceasefire agreement between the Myanmar armed forces and ethnic armed groups broke down in 2011.