Clean air blows in for a brief visit

Heavy smog expected to put chokehold on northern cities, stick around until midweek

Beijing residents got a brief respite from a spate of smog on Sunday morning, when the chilly air went from hazardous to good. But the pollution will come back stronger on Monday and engulf the capital and its southern neighbors again for three days, the national weather authority said.

Beijing saw readings of PM2.5 - hazardous particulate matter with a diameter less than 2.5 microns - drop dramatically from 106 micrograms per cubic meter on Saturday evening to 24 by 8 am. on Sunday, according to the Beijing Municipal Environment Monitoring Center. It started creeping back up and was at 64 by 4 pm. The cutoff for "good" air is 75.