The first frost of the season was observed in Seoul on Monday as unseasonably cold weather continued for most parts of the country in the morning, the state weather agency said.

Morning lows hovered around 5 C across the country, slightly up from Sunday, when some areas experienced record-low temperatures for mid-October, the Korea Meteorological Administration (KMA) said.

The first frost of this fall was spotted in Seoul and nearby Suwon, the agency said.

The weather is expected to warm up in the afternoon as the cold front weakens and warm southerly winds prevail.

Daytime highs are forecast to range from 13 C to 19 C, lower than the average of 19 C to 22.5 C but higher than Sunday's 10.2 C to 16.7 C, the KMA said.

On Sunday, the morning low in Seoul came to 1.3 C, the lowest for mid-October since 1957. The unseasonable cold snap is expected to continue through this week, the agency said. (Yonhap)