People who have been sleeping outdoors since the earthquake had their belongings completely soaked through during a downpour and strong winds on Saturday evening, according to Tun Tun at the UN Development Programme UNDP for AFP.
Temperatures are reaching up to 37 degrees and more rain is expected.
The weather is extremely extreme, he says.
During the earthquake, numerous buildings and bridges collapsed, and roads were destroyed in several parts of the country. The most severe damage has been reported in the city of Sagain near the epicenter of the earthquake, and in Mandalay, which is Myanmar's second-largest city with 1.7 million inhabitants.
Many have had their homes completely destroyed, and others dare not live in buildings that have become unstable due to the earthquake.
Nearly 3,300 people have been confirmed dead in the earthquake with a magnitude of 7.7 that occurred just over a week ago. 4,671 people were injured, and over 200 are missing.
According to aid experts, rainy conditions and heat can also increase the risk of disease outbreaks in camps where those affected have taken shelter.
Food, water, and electricity repairs are needed immediately, says Tom Fletcher, head of the UN's disaster relief organization Ocha, in a video clip from Mandalay.
The earthquakes continue. We had another earthquake of 4.9 last night, people are living with the trauma all the time, he says.
