A cool start to Sunday, followed by a large temperature swing

Sunday, October 4, is expected to bring a chilly start to parts of South Korea, particularly inland and mountainous areas of Gangwon Province. Across central parts of the country and inland North Gyeongsang Province, the gap between daytime and nighttime temperatures could reach around 15°C.

A large daily temperature range means it may feel quite different outside between early morning and afternoon. People heading out in the morning may need an extra layer, while those out later in the day could find the same clothing too warm.

Forecast for October 4: Morning lows are expected to range from 8°C to 18°C, while daytime highs are forecast at 22°C to 27°C.

Expected temperatures in major cities

Forecast morning temperatures include 9°C in Chuncheon, 14°C in Daejeon and Daegu, and 15°C in Seoul, Suwon, and Gwangju. Incheon is expected to start at 16°C, while Busan is forecast to be milder at 18°C.

These are forecast lows, not temperatures expected to last through the day. With daytime highs reaching the low to upper 20s Celsius, the contrast may be especially noticeable for people commuting early or spending much of the day outdoors.

Clouds increase, with rain arriving in several regions

Skies across the country are expected to be partly cloudy at times, then gradually become cloudier from Sunday evening. Rain is forecast to begin at different times depending on the region, so conditions may change during the day rather than all at once.

Jeju Island is expected to receive less than 5 millimeters of rain from Saturday night through Sunday morning. Busan, Ulsan, and the east coast of North Gyeongsang Province are forecast to see 5 to 10 millimeters from Sunday morning through the afternoon.

Rain forecast from Sunday night

From Sunday night, rain is expected in the Seoul metropolitan area, northern inland parts of Gangwon Province, South Chungcheong Province, and the northwestern part of North Jeolla Province. Some of these areas may continue to see rain through Monday morning, October 5.

Rainfall amounts can differ from place to place, and the forecast does not mean every neighborhood will receive the same amount. Residents should check local updates before traveling, especially if plans involve an evening drive or outdoor activity.

Thunderstorms and small hail are possible

In areas receiving rain through Monday morning, gusty winds, thunder, and lightning are possible. Thunderstorms are rain clouds that can produce sudden downpours, strong winds, and lightning, sometimes over a short period.

Small hail—little balls or lumps of ice formed inside storm clouds—may fall in parts of the central west coast and the northern inland areas of Gyeonggi and Gangwon provinces. Hail is expected only in some locations, but it can still be disruptive for people outside and may briefly affect road conditions.

What to keep in mind: If storms develop, move indoors when possible and avoid exposed areas. Drivers should be prepared for sudden drops in visibility and wet roads.

Practical steps for the changing conditions

The combination of a cool morning, warmer afternoon, and possible evening rain makes it useful to plan for more than one kind of weather. A light layer that can be removed later may help with the temperature shift, while an umbrella or waterproof outer layer could be useful in regions expecting rain.

  • Check the latest local forecast before leaving, especially for evening plans.
  • Allow extra travel time if rain or thunderstorms are expected along your route.
  • Be alert to lightning and gusty winds near thunderstorms.
  • In areas where small hail is possible, consider sheltering vehicles and avoiding exposed outdoor spaces.

The forecast at a glance

Sunday is expected to start cool in parts of the country, with the strongest chill in inland and mountainous Gangwon. Day-night temperature differences of about 15°C are forecast in central regions and inland North Gyeongsang, while rain is expected to spread into several regions from Sunday night.

The main change to watch is the transition from a relatively mild, partly cloudy day to unsettled conditions after dark. Rain, gusts, thunder, lightning, and isolated small hail are possible in some areas through Monday morning.