Due to shifting wind and weather conditions, a massive sand and dust storm will be blown back to northern China and hit central, northern and northwestern parts of the country, the National Meteorological Center said on Wednesday.

The sandstorm, which had shrouded Beijing in thick brown dust on Monday, moved away from the capital on Tuesday but continued to sweep through many areas, including the Xinjiang Uygur, Inner Mongolia and Ningxia Hui autonomous regions, as well as the provinces of Qinghai, Gansu, Shaanxi, Shanxi, Hebei, Shandong, Henan and Hubei.

Most of those regions will be affected by the sandstorm until Thursday, according to the center, which reminded people in affected areas to be prepared and close windows and doors.

"People are advised to wear masks and other protective gear to prevent possible damage to their eyes and respiratory tract," an earlier notice from the center said.

The notice also warned drivers to pay more attention to road safety due to poor visibility.

On Monday, the sandstorm from neighboring Mongolia hit 12 provincial regions in northern China and resulted in the suspension of school classes and the cancellation of many flights.

Remote sensing images showed that the storm covered an area of 466,000 square kilometers.

On Tuesday, the National Meteorological Center renewed a sandstorm alert for northern, central and eastern parts of the country.

At 9 am on Monday, the level of PM10－particulate matter of 10 microns or smaller－in Beijing had reached 8,108 micrograms per cubic meter, according to the Beijing Ecological and Environmental Monitoring Center.

By 10 am on Wednesday, the average concentration of PM10 in Beijing was 285 micrograms per cubic meter.

The National Meteorological Center, citing a change in wind and weather conditions, said on Wednesday morning that the sandstorm would return on Wednesday afternoon and was expected to be gone on Thursday.

On Wednesday night, mountainous areas in Beijing were to have rain, with rainfall expanding to urban areas of the capital late on Friday, according to the center.

Factors leading to sandstorms are complex, said Zhou Bing, chief expert at the China Meteorological Administration's National Climate Center.

Over the past winter, days of precipitation in Mongolia and many regions of North China were only half of what they were during the same period last year, which increased the possibility of sandstorms, he said.

"The heavy sandstorm this time was also influenced by strong winds from Siberia, Inner Mongolia and the Mongolian Plateau, as well as rising temperatures, which makes the sand more exposed and prone to being carried by the wind," Zhou said.

He said sand and dust storms have been much less frequent in northern China. According to the National Climate Center, the region had sand and dust storms about 10 times annually in the past decade, a significant drop from 17 times a year between 1981 and 2010.

Zhou also emphasized the environmental improvements resulting from the country's green efforts in recent decades.

China has made remarkable progress in improving vegetation coverage, which has greatly contributed to reducing sandstorms.

Last year, the country planted 6.77 million hectares of forest and brought more than 2 million hectares of sandy land under control through improving vegetation, according to the National Greening Commission.

Satellite surveillance conducted by the National Forestry and Grassland Administration indicates that China's sandy and desert areas have each been reduced by about 2,000 square km a year this century.

The administration conducts the survey every five years. The latest survey is about to be completed, and its results are expected to be published by the end of the year, said Sun Tao, director of the administration's desertification survey center.

He added that current information shows that the two areas will continue to shrink.

Xinhua contributed to this story.