A cold air mass is sweeping across China from north to south, with temperatures expected to fall in eastern and central parts of the country, the National Meteorological Center forecast on Wednesday.

Temperatures in Central, East and South China are forecast to dive by up to 12 C from Wednesday, accompanied by strong winds of up to 88 kilometers per hour, the center said.

It issued an orange cold warning nationwide on Tuesday, the highest level in its three-tier system. The last orange warning occurred in 2016.The center lowered the warning to yellow on Wednesday.

Weather.com advised people in 27 provincial-level regions on Tuesday to wear padded pants to counter the cold.

A blue snowstorm alert, the lowest level, was issued in East China's Anhui province on Tuesday.

As the cold wave moved southward to East and South China, orange farmers in Sichuan and Zhejiang provinces adopted anti-freezing measures like covering the fruit or harvesting it in a hurry, China Central Television reported.

The cold wave caught Zhao Songyuan, an orange farmer in Shengzhou, Zhejiang province, unprepared. As the temperature fell below -6 C on Tuesday, he hired about 30 workers to harvest the tens of thousands of oranges on his farm to prevent them from freezing.

"In normal years, we harvest fruit in late January," he told CCTV. "The sudden cold wave brought this year's harvest forward."

On Tuesday, a short video that went viral online showed piles of chicks frozen to death in a greenhouse in Yancheng, Jiangsu province, after strong winds tore away its covering.

The owner said it was due to the weather and the substandard greenhouse he had built. He lost about 8,000 chicks.

Early on Sunday, the temperature in the Greater Hinggan Mountains of Northeast China's Heilongjiang province hit -44.5 C, the lowest in the region this winter, the meteorological service in the mountains said. Photographs taken by China News Service showed white fog caused by condensation shrouding the region and reducing visibility.

Sun Jun, the National Meteorological Center's chief forecaster, said cold air from high in the Mongolian Plateau that moved eastward and southward caused the freeze in the north and will expand its influence nationwide until Thursday.

"This round of the cold wave will be tougher than the same period in normal years as temperatures will even drop below zero in the provinces of Hunan and Jiangxi, the southernmost places that subzero temperatures will have reached this winter," he said.

Sun said that as the main cold wave arrives in South China on Thursday, North China will warm up a little. Southern areas will experience a longer period of chilly weather than in the north, with the cold spell continuing through the opening weeks of 2021.

The center warned people to wrap up warmly and beware of catching cold.