Myanmar is a vast and poor country, where communications and infrastructure are already weak, prompting the United Nations to warn that a full picture of the scale of the disaster may not emerge for days.
Authorities have declared the four worst-hit areas in central and western Myanmar "national disaster-affected regions".
In the impoverished northern Sagaing Region, residents said the flood waters caught them off-guard as floods swept into villages, swamping homes and fields.
"There was no warning... we thought it was normal (seasonal flooding)," Aye Myat Su, 30, told AFP from a monastery being used as a temporary shelter in the regional capital of Kalay.
"But within a few hours, the whole house was underwater. My husband had to get onto the roof as there was no way out."