The smog is back in Beijing, blanketing the Chinese capital again as the city struggles to deal with the choking pollution.

The smog is stretching beyond the city and into much of northern China, with authorities warning that heavy pollution will cause problems for residents this upcoming week and into New Year’s Day, according to a South China Morning Post report.

A cold front arriving this weekend failed to move the smog out of the area, so it will stick around for a little while longer.

In responds, Beijing authorities are putting heating limits into place at government buildings, offices, shopping malls, and many other venues. It did not specify when heating could return to normal. Authorities are trying to get residents to cut down on their use of heating and electricity in general.

It’s the second time there’s been a red alert for smog this month. It’s gotten so bad that schools have been forced to close and the government has had to limit the use of cars.

Mountains north of Beijing often block wind from the south, causing the massive amounts of coal and other burning pollutants to settle and expand in the region.

Beijing residents will be exposed to pollution levels of up to 350 micrograms per cubic meter — by comparison, the World Health Organization recommends no more than 25 micrograms per cubic meter.

According to the U.S. Environmental Protection Agency, “breathing smoggy air can be hazardous because smog contains ozone, a pollutant that can harm our health when there are elevated levels in the air we breathe.” It notes that ozone is odorless and colorless, and naturally occurs in the Earth’s upper atmosphere, but it’s bad for humans to ingest.