BEIJING -- Visibility is low in Beijing on Wednesday as the municipal observatory hoist a blue alert on dust weather.

The blue alert, or the lowest level in the four-tier weather alert system, was issued at 5:35 am by the Beijing Meteorological Service.

It said the floating dust and sand deriving from Mongolia hit Beijing from 6 a.m. Wednesday, and will continue to affect the capital city in the whole day.

Beijing has maintained an orange alert on smog, or the second only to red alert, since Monday.

On Wednesday, the average level of slightly larger PM10 particles topped 1,988 micrograms per cubic meter, while that of PM2.5 reached 193 micrograms per cubic meter in the urban area, according to data from Beijing municipal environmental monitoring center.