The National Meteorological Center issued dual warnings on Wednesday for torrential rain and sandstorms as volatile weather conditions are expected to affect parts of the country.

The center issued a blue alert for heavy rain at 6 am, the lowest level in China's four-tier warning system, forecasting downpours from Wednesday morning to Thursday morning across parts of South China and Jiangxi province.

Parts of Guangdong and Jiangxi provinces, Hainan Island, and the Guangxi Zhuang autonomous region are expected to experience heavy to torrential rainfall, the center said.

Localized rainstorms with precipitation of 100 to 180 millimeters are forecast in northeastern Guangxi and along its southern coast, as well as in northwestern Guangdong and along its southwestern coast, according to the center.

The center warned that of hourly rainfall in some areas could exceed 70 mm, accompanied by severe convective weather including thunderstorms and gale-force winds.

Chen Boyu, chief forecaster at the center, said the latest round heavy rain was mainly caused by a circulation pattern resembling that of the plum rain season.

Since Friday, heavy rainfall has affected large parts of China, the center said. From 8 am on Friday to 8 am on Tuesday, parts of Sichuan province, Chongqing municipality, and Hubei, Hunan, Guizhou, Guangdong and Hainan provinces, as well as Guangxi, recorded cumulative precipitation exceeding 100 mm.

Chen said two key factors were driving the rainfall. The subtropical high over the South China Sea was positioned unusually far north, continuously transporting warm, moist air from the Indochina Peninsula and the South China Sea into southern China. Meanwhile, a Mongolian cyclone pushed cold air southward.

As the cold and warm air masses converged, eastward-moving plateau troughs provided favorable lifting conditions and intensified atmospheric instability, creating a stable and moisture-rich precipitation system, he said.

"This has produced a prolonged period of heavy rain featuring persistent rainbands and intense localized precipitation," Chen said.

Also on Wednesday, the center renewed a blue sandstorm alert, warning that blowing sand and floating dust would affect parts of northern and northwestern China from Wednesday morning to Thursday morning.

Driven by strong winds associated with a cold air mass, the weather is expected to affect eastern and southern parts of the Xinjiang Uygur autonomous region, northwestern Qinghai province, western Inner Mongolia autonomous region, western Gansu province and western Ningxia Hui autonomous region. Localized sandstorms are forecast in eastern Xinjiang and western Inner Mongolia.