The Chinese National Meteorological Center (NMC) predicted on Thursday that rains might sweep the quake-hit regions of the southwest next week and trigger landslides and mud-rock flows.
The rain would also add to the risks of "quake lakes" formed by landslides that blocked rivers, said meteorologists.
"There were 33 such lakes in Sichuan. Three quake lakes, in Anxian, Qingchuan and Beichuan counties, were the biggest," said Zhu Bing, deputy head of the water resources authority in Sichuan Province.
He said the province had been closely monitoring such lakes and made emergency response plans, including evacuating people to safer places when necessary and blasting or digging of sluices to discharge water.
The southwestern province was the hardest hit in the 8.0-magnitude earthquake on May 12.
Liu Yuan, deputy head of the geological environment department of the Ministry of Land and Resources, said the quake lakes, formed as water was blocked from following river beds by rock and mud slides set off by the earthquakes, were very dangerous.
The water level of some quake lakes had risen, threatening vast areas, said Liu. The Ministry of Land and Resources and the Ministry of Water Resources jointly sent experts to assess the condition of the lakes. The experts departed from Beijing for the sites on Thursday, Liu added.
According to Yin Yueping, deputy chief engineer with the China Geological Survey, efforts are being made to evacuate people living downstream of the lakes. He did not say how many people were affected.
The NMC said Sichuan and the southern part of Gansu would see cloudy weather on Friday and Saturday with daily highs of 27 to 32degrees Celsius.
As temperatures in tents were usually 2 to 3 degrees higher than the outside, experts called for intensified disinfection measures to prevent disease.
The death toll from the May 12 earthquake, China's worst in more than 30 years, rose 9,798 to 51,151 as of 10:00 a.m. Thursday, with 288,431 people injured and 29,328 missing, according to the emergency response office of the State Council, or the Cabinet.