Severe weather warnings were in place across swathes of China on Wednesday as temperatures plummeted across the south and Beijing shivered in snowy conditions.

Authorities renewed an orange alert -- the highest in the country's three-tier system -- warning that average temperatures in the south could fall by six to 12 degrees Celsius (43 to 53 Fahrenheit) by Friday.

In some areas, the mercury could plunge by over 20C, the National Meteorological Center (NMC) said on social media.

State news agency Xinhua said the NMC had "called on local governments to take precautions against the cold weather, advised the public to keep warm, and called for necessary measures to protect crops and aquatic products".

In Beijing, where temperatures hovered around freezing on Wednesday, residents awoke to find the capital blanketed in white following an overnight snowfall.

Traffic slowed to a crawl on the city's highways, while snow-dusted pavements proved treacherous for commuters and cyclists.

Municipal authorities said up to 4.1 centimetres (1.6 inches) of snow had fallen in some suburban areas and issued a warning over icy roads.

"It is recommended that residents... stagger their travel, use public buses and subways, drive their own cars slowly and pay attention to safety," the city government said in an online statement Tuesday evening.