Short sleeves still work during the day, but long sleeves are needed at night. Temperatures are set to fall sharply this week, with Seoul's morning lows dipping into single digits by early October.
The morning low in Seoul was 19.2 C on the 28th, hovering around 20 C, according to the Korea Meteorological Administration. Daytime highs ranged from 24 C to 29 C, relatively mild, though dense fog lingered until the morning in parts of the inland regions and along the east coast, cutting visibility to less than 200 meters in some areas. Ozone levels were forecast to reach unhealthy concentrations in the afternoon in South Chungcheong Province, South Jeolla Province, Busan, Ulsan and South Gyeongsang Province. Residents were advised to watch ozone levels when going outdoors.
The real drop begins the following day. Seoul's low and high on the 29th were forecast at 15 C and 27 C. Daytime temperatures still climb to 27 C, but mornings and evenings turn noticeably cool.
The weather agency said daily temperature swings could widen to as much as 15 C from the 29th, mainly in inland areas nationwide. On the 30th, an incoming trough will bring 5 to 10 millimeters of rain to central regions and Jeonbuk State, followed by mostly clear skies through Oct. 3.
The decisive turning point comes on Oct. 1. Cold air moving south from the north is expected to push temperatures down by about 5 C, mainly in central regions. As that effect carries over, Seoul's low and high on Oct. 2 were forecast at 9 C and 21 C. Compared with the 29th, when the low was 15 C, that marks a 6 C drop in morning temperatures in just three days.
Short sleeves may still suit the daytime, but a light jacket will be essential in the mornings. On Oct. 4, another trough will form, bringing afternoon rain to parts of the greater Seoul area and the western inland region of Gangwon State.
