People rush to work as they are caught in heavy snow amid the late-season cold snap in Gwangju, Tuesday. Yonhap

An unexpectedly heavy snowfall hit Korea early Tuesday, disrupting morning commutes and causing flight delays.

A heavy snow warning was issued for most regions of the country, marking the first time in seven years that such an alert has been extended nationwide in mid-to-late March. In Seoul, the warning was the latest in the season ever recorded in 26 years of data collection.

According to the Korea Meteorological Administration (KMA), snowfall reached 14 centimeters from 8 p.m. Monday to 6 a.m. Tuesday in Cheorwon, Gangwon Province, while Uijeongbu and Pocheon in Gyeonggi Province recorded 13.6 and 12.7 centimeters, respectively. Northern Seoul also saw more than 10 centimeters of accumulation.

The unusual snowfall was triggered by a strong polar low-pressure system, which brought Arctic air as cold as minus 40 degrees Celsius into the region, the KMA explained.

This heavy snowfall caused major disruptions across the peninsula.

According to Korea Airports Corp., four flights were canceled as of 8 a.m. — one each from Gimpo, Jeju, Yeosu and Wonju airports. In addition, five flights were delayed at Incheon International Airport.

The cancellations were attributed to strong winds and ongoing de-icing operations to remove snow and ice from aircraft, the corporation said.

Commuters also faced severe traffic congestion and overcrowded subway trains during the morning rush hour.

"I had to skip a train because it was too crowded," an office worker surnamed Han in her 20s, who commutes from Incheon to Seoul's Mapo District, said.

Another office worker in his 30s surnamed Kim, who travels from Bundang District in Seongnam, Gyeonggi Province, to Jongno District in central Seoul, said, "I left home 30 minutes earlier than usual after hearing about the heavy traffic."

Train operations on Uijeongbu's U Line light rail transit system were temporarily suspended across all sections at 5:15 a.m. due to the snowstorm.

Service resumed at 7:25 a.m. after snow removal efforts, but the disruption left many commuters stranded during the busy morning rush hour.

KORAIL operated 14 additional subway trains during the morning rush hour to ease commuter congestion. The extra services included six trains on Line 1, three on the Suin-Bundang Line and two on the Gyeongui-Jungang Line.

Meanwhile, icy roads also led to multiple traffic accidents.

In South Jeolla Province, a 42-vehicle pileup occurred on the Namhae Expressway at around 10:40 a.m. A total of 11 people sustained minor injuries and were taken to hospitals, but no serious injuries were reported.

The accident was triggered when a 45-seat bus skidded on the snow-covered road, causing a pileup.

Spring festivals also faced issues due to unseasonal weather. The Gurye Sansuyu Festival, one of South Jeolla Province's signature spring flower festivals, experienced unexpected snowfall just a day after its opening.

While the festival is set to run until Sunday, the inclement weather has disrupted some scheduled events.