Winter is coming, that’s for sure. The northeastern city of Harbin today ushered in the season with smog so thick that visibility was reportedly limited to 10 meters in places. Classes were canceled, roads closed, and planes grounded.

State media said the PM 2.5 reading (which measures the level of harmful particulate matter in the air) “exceeded” 500. A Reuters report put the figure at 1000, or 40 times higher than what the World Health Organization deems safe. Photographs from the city show air so murky it would be easy to mistake Monday morning for deep, dark night.

The shutdown in Harbin is sure to worry residents of northern China as the region heads into what promises to be another long, dirty winter. China’s northeast is plagued year-round by air pollution, the result of factory emissions and massive growth in the number of vehicles on the road. Things get worse, however, when the heaters crank up, increasing the amount of coal that gets burned. Harbin’s current smog comes the day after the city turned on its heaters.

It’s not the first time bad air has brought a Chinese city to a halt. Last year, Beijing was gripped by a weeks-long airpocalypse that sent families scrambling for cover and bolstered sales of face masks and air-purifiers. By choking the nation’s capital in its embrace, that haze helped put pollution on the national agenda, with officials finally recognizing, and promising to address, the problem.

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