China’s capital Beijing has broken its record for hours of sub-zero temperatures in December dating back to 1951, after a cold wave swept swathes of the country and brought blizzards in its wake, sending temperatures towards historic lows.

Northern and northeastern parts of the country have experienced a record-breaking chill since last week, with some areas in the northeast hitting minus 40 Fahrenheit and below as biting cold air flowed down from the Arctic.

As of Sunday, a weather observatory in Beijing had recorded more than 300 hours of below-freezing temperatures since Dec. 11, the most for the month since records began in 1951, according to state-backed Beijing Daily.

The capital has also endured nine consecutive days of temperatures below minus 10 C (14 F) in this period, the Beijing Daily added.

Several cities in the central Chinese province of Henan, southwest of Beijing, are in the grip of a winter heating supply crunch, with thermal power suppliers in the city of Jiaozuo under pressure to ensure supplies.

Heating boilers at JiaoZuo WanFang Aluminum Manufacturing, one of the major suppliers in the city, have broken down, leaving some areas in urgent need of more heat supply, state media reported on Sunday.

The supplier is scrambling to fix the malfunction and expects to resume supply on Dec. 26, state media reported, without specifying the number of boilers that have broken down.

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JiaoZuo WanFang Aluminum did not immediately respond to an emailed request for comment from Reuters.

The city will suspend heat supply for most businesses except essential service providers such as hospitals and senior centers to prioritize residential heat usage. However, some residential compounds will still be affected during the device maintenance period, the media reports added.

Two other cities in Henan — Puyang and Pingdingshan — have already suspended heat supply to government departments and administrative institutions to prioritize residential usage, the local governments said, citing extremely cold weather.

The weather forecast shows temperatures in the three cities hitting sub-zero on Sunday. Temperatures in several other areas in Henan would plunge to a low of minus 15 C (5 F) over the weekend, the central province’s weather authority said on Saturday.

Warm air is expected to flow from the country’s north to south lifting temperatures from the weekend.

As of 2 p.m. (0600 GMT) on Sunday, temperatures in many areas in central and eastern China had rebounded somewhat, with temperatures in some areas rising by more than 10 C, China’s weather authority said.