Most Beijingers woke up on Monday to find, to their surprise, that a "yellow blanket" has covered up everything in the open air: from window sills, cars and the ground to every single leaf on the trees.

A woman walks past a car parked in the open air and covered by dust in Beijing April 17, 2006. Dusty weather is a headache for Beijing in spring. Experts advised residents stay indoor or wear masks when going out for their health as the dusty weather continues today. [Xinhua]

"As if the desert has crawled to Beijing overnight," said ZhangRui, a citizen in Chaoyang District in eastern Beijing.

He was not exaggerating -- Zhang said he spent at least 15 minutes dusting the sand off his Jetta sedan.

A sandstorm hitting the China-Mongolia border Saturday and Sunday started to affect Beijing at midnight on Sunday and by daybreak, the city had turned yellowish.

"Unlike the particulate matter that often exists in Beijing's air, the suspending granules hitting the city today are bigger, though still less than 100 microns in diameter," said Wang Xiaoming, an official with the municipal environment protection bureau. "That's why we feel sand is raining down."

The particulate matter that often hovers over Beijing is mostly less than 10 microns in diameter, he added.

Wang said this is the eighth, as well as the worst, sandy weather that attacks from outside Beijing this year.

The bureau forecast at 9:00 a.m. that the city's air quality will be level V or hazardous on Monday, with pollution reading over 301.

The municipal government launched a pollution control scheme Sunday night hoping to lessen the impact of the sandy weather. The city has sent sprinklers to wash urban roads and construction sites have been told to halt earthwork.

The city's meteorological bureau predicts drizzle in northern Beijing on Monday night and says the wind scale will reach five on Tuesday. But neither will be strong enough to drive away the dust, which will probably stay until Tuesday evening.

From Jan. 1 to April 17, Beijing has reported 56 "blue sky days", with excellent or fairly good air quality and pollution reading less than 100, 16 days less than the same period of 2005.

Sandstorms could easily occur at places with little rainfall, scarce vegetation and frequent gales, said Qiao Lin, an expert in China Meteorological Administration (CMA).

Northern China experiences sandstorms almost every spring. The situation is worsened by higher temperature this spring and the prolonged drought in northern China, according to Qiao.

China launched an afforestation project in 2000 in Inner Mongolia Autonomous Region, which is blamed as source of sandstorm, targeting sandstorm threatening Beijing and Tianjin, but it is difficult to contain the intensified desertification.