SEOUL - With heavy snowfall jamming the roads in Seoul, Singaporean Dominic Phua spent nearly an hour walking home after work.

The 30-year-old marketing director saw a biker zoom by covered in snow, cars skidding even while moving at tortoise pace, and two buses with a car stuck between them.

"The snow suddenly came and hit so fast and hard," he told The Straits Times on Thursday (Jan 7).

"The roads were too slippery and drivers in Seoul were just not prepared, with no winter tyres."

A cold snap has gripped South Korea, with a warning issued for the southern Jeju island for the first time in 57 years and overnight snowfall nationwide from Wednesday causing train delays, flight cancellations and minor traffic accidents.

Temperatures in Seoul plunged to minus 16.1 deg C on Thursday morning, with a wind chill of minus 25.3 deg C, according to the Korea Meteorological Administration (KMA).

The mercury is expected to drop as low as minus 20 deg C by Saturday and is expected to rebound above zero only next Tuesday.

The city's southern Seocho district got the most snow, 13.7cm from Wednesday evening to early Thursday morning.

In the more rural north-eastern Gangwon province, Mount Seorak recorded minus 29.4 deg C.

A cold wave warning was issued nationwide on Wednesday night - the first time in three years.

The KMA said the plummeting mercury is caused by cold air flowing down from nearby Siberia, but some experts also attributed it to a lower carbon footprint last year, with factories shutting down during the coronavirus pandemic.

Heavy snow continued across the nation yesterday, causing at least 86 flights to be cancelled at the Gimpo International Airport, west of the capital. Incheon International Airport also reported seven flights cancelled as at 4pm.

Traffic on Thursday morning was also hit, with severe congestion reported. Wary of slippery roads, cars moved at an average speed of 19kmh.

Subway trains were delayed by breakdowns, and some doors got stuck in the freezing cold.

Prime Minister Chung Sye-kyun has issued an emergency order to speed up snow removal work to avoid further traffic disruptions.

More than 8,000 vehicles have been deployed along with some 17,000 personnel to clear the snow.

The cold wave came as South Korea continues to battle a third Covid-19 wave that has pushed the total number of cases up to 66,686.

The health authorities said the infection curve is finally starting to flatten due to tightened social distancing rules, including a ban on social gatherings of more than four people, and aggressive preemptive testing.

Wednesday's snowfall was welcomed by many people who took to social media to post selfies and videos.

Children could be heard laughing as they dashed out to make snowmen or sled on small slopes in the neighbourhood.

Mr Phua, who has lived in Seoul for five years, said this is the first time that he has witnessed such heavy snowfall in the city.

He decided to walk home as the road traffic in the posh district of Gangnam, where he lives and works, was hardly moving.

"Plus the snow was quite a rare sight so I just wanted to enjoy the walk home," he said.

Along the way, Mr Phua saw people slipping and falling. He also saw people pushing cars and buses that had stalled in the snow.

"I felt really bad for the people who got stuck," he said, adding that some of his friends took up to six hours to get home.

"But it was also quite funny, like when I saw this delivery guy riding a scooter with his whole body covered in snow."