While the country faces chilly weather on Thursday with the onset of winter based on the lunar calendar, Busan has yet to burst into autumn gold and amber, leaving foliage spots still verdant, the state weather agency said.

According to the Busan branch of the Korea Meteorological Administration, as of Wednesday, South Korea's second-largest city has not officially begun its autumn foliage season, nearly a week behind the city’s average, with ginkgo trees typically changing color by Nov. 1 and maple trees by Nov. 2.

Last year, the foliage of ginkgo and maple trees turned by Nov. 5 and Nov. 7, respectively.

The KMA defines the “beginning” of autumn foliage as the point when 20 percent of leaves on a mountain turn fall colors, while the “peak” is reached when 80 percent of the leaves change.

Experts believe that prolonged warm weather has delayed the autumn foliage peak, raising the possibility of early leaf drop before the leaves fully bloom into vibrant colors.

Busan’s daytime high is expected to hover around 20 degrees Celsius until next week. Morning lows, except for Thursday and Friday, are forecast to stay above the 10-degree mark through next week.

Seoul observed its first frost this autumn on Wednesday, four days later than the average but one day earlier than last year. Other parts of the nation, including Cheongju, Daejeon and Chuncheon, also saw their first frost on the same day.