China's northernmost city, Mohe in Heilongjiang province, issued a red alert for a cold snap on Monday, its first since records began, China News Service reported.
The city meteorology authority said the temperature plunged by 22.1 C from Monday to Tuesday.
Monday saw a low of -19 C, but on Tuesday the mercury fell to -41.1 C, triggering the red alert.
The lowest temperature in Mohe is expected to hover around -40 C on Wednesday before rising slightly on Thursday.
The city, which borders Russia's Siberian region, has an average temperature of -5 C year-round.
