Beijing issued its second red alert for smog, the highest-level warning, on Friday as the national weather authorities said that more smoggy days are ahead due to higher temperatures and a lack of snow this winter.

Heavy smog is forecast to blanket Beijing on Saturday and is expected to last for four days, forcing the government to adopt the strictest measures to ease pollution. These include reducing by half the number of vehicles on the roads based on odd and even license plate numbers and shutting down industrial operations.

Wang Bin, head of the Emergency Response Department of the Beijing Bureau of Environmental Protection, said emergency measures will be in effect from 7 am on Saturday until midnight on Tuesday.

It will be the fourth spell of severe smog in Beijing since November, with pollutants expected to reach the most hazardous level on Tuesday, said Li Yunting, director of the Atmospheric Forecast Department of the Beijing Environmental Monitoring Center, on Friday.

A report by the National Climate Center attributed the frequent smoggy weather in the northern regions to higher temperatures and a decrease in precipitation of up to 50 percent this winter compared with an average year.

The northern regions have also had less wind and higher humidity, and these conditions have helped worsen air pollution, the report said.

The northern areas affected include Hebei, Henan, Shandong and Shanxi provinces, as well as Beijing and Tianjin.

In addition to Beijing, Handan in Hebei also issued a red alert, and many other cities in the province issued orange alerts, the second-highest level.

Li said the smog should end on Wednesday, when strong winds are expected to sweep the area.

Wang also called for regional cooperation in curbing pollution.

In the last spell of smog that hit northern areas, readings for the concentration of PM2.5 - particulate matter with a diameter of less than 2.5 microns that can penetrate the lungs and harm health - reached over 1,000. That is a dozen times more than the national safety standard.

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