August 20 Weather: Showers in Southern Gyeonggi, Chungcheong and Southern Regions…Daytime Highs of 33°C

On Thursday, 2026-08-20, showers are not expected in every part of the country. Scattered showers are forecast across southern Gyeonggi Province, the Chungcheong region and southern parts of the country between morning and evening, while Jeju Island is expected to receive rain from early morning through the afternoon. Nationwide morning lows will range from 21 to 26°C, with daytime highs of 29 to 33°C.

Because the areas and times when umbrellas will be needed vary considerably, it is important to check whether your specific location is included in the forecast rainfall area rather than planning your day based solely on a general forecast of 'scattered showers nationwide.'

Where and When Are Showers Expected on August 20?

The main areas forecast to receive showers are southern Gyeonggi Province; Daejeon, Sejong, South Chungcheong and North Chungcheong; North Jeolla, Gwangju and South Jeolla; and Daegu, North Gyeongsang, Busan, Ulsan and South Gyeongsang. The forecast window runs from 9 a.m. to 9 p.m.

Expected rainfall amounts vary considerably by region.

Southern Gyeonggi: 5–20 mm

Daejeon, Sejong, South Chungcheong and North Chungcheong: 5–40 mm

North Jeolla, Gwangju and South Jeolla: 5–60 mm

Daegu, North Gyeongsang, Busan, Ulsan and South Gyeongsang: 5–60 mm

Although all these areas are under a 'shower forecast,' the upper limit for southern Gyeonggi is 20 mm, compared with up to 60 mm in the Jeolla and Gyeongsang regions. According to the author's calculation, the difference between the maximum forecast amounts is 40 mm. This figure is obtained by subtracting 20 mm from 60 mm and does not mean that 60 mm of rain will necessarily fall at any particular location.

Showers can vary significantly from place to place, meaning that even within the same city, some neighborhoods may receive rain while others receive little or none. If your plans extend from morning into the evening, it is safer to check the latest neighborhood forecast and weather radar immediately before leaving.

Will Seoul and Gangwon Province Also Receive Showers?

According to the nationwide short-term forecast for August 20, showers are not forecast across the entire Seoul metropolitan area, including Seoul itself. Southern Gyeonggi is the only part of the metropolitan area explicitly identified as a shower zone.

In parts of the metropolitan area, southern Gangwon's inland and mountainous areas, and the Chungcheong region, occasional raindrops amounting to less than 0.1 mm may occur between early morning and morning. Raindrops totaling less than 0.1 mm are not the same as an afternoon shower forecast, so the two should be distinguished.

Sky conditions will also differ by region. The metropolitan area and Gangwon Province are expected to be mostly cloudy, while the rest of the country will generally see overcast skies.

Rather than assuming that heavy showers will continue throughout the day in Seoul, it is more accurate to consult the detailed local forecast. Conversely, anyone traveling to southern Gyeonggi should account for the possibility of showers from 9 a.m. through the evening.

Jeju Island Is Forecast to Receive Rain, Not Showers

Jeju Island differs from other regions in both the type and timing of precipitation. Rain is forecast across parts of Jeju Island from 0 a.m. to 6 p.m. on August 20, with expected rainfall of 10–40 mm.

Southern Gyeonggi, Chungcheong and southern regions have shower forecasts, while Jeju has a rain forecast. Anyone planning travel or outdoor activities should avoid assuming that the precipitation will be limited to a brief afternoon shower.

Because Jeju's forecast rainfall window extends from early morning into the afternoon, travelers should check the latest hourly forecasts for their specific locations immediately before departing, particularly when planning airport transfers, rental-car journeys or outdoor sightseeing.

Daytime Highs Still Reach 33°C Despite the Rain

Nationwide morning lows on August 20 are forecast at 21–26°C, with daytime highs of 29–33°C. Despite the forecast showers and rain, daytime temperatures in some areas are expected to climb from around 30°C to as high as 33°C.

In particular, it would be difficult to conclude that the entire day will be cool simply because rain is expected. The Korea Meteorological Administration expects hot weather to continue for the time being.

The apparent temperature differs from the actual air temperature. It is a measure of how hot people feel, taking into account humidity and wind as well as air temperature. Higher humidity can make the same air temperature feel hotter.

The medium-range forecast also indicates that many areas nationwide will experience hot days with maximum apparent temperatures approaching 33°C, while some locations may experience tropical nights. Anyone planning extended outdoor activities during the daytime should prepare for both rain and heat.

Compared With 19, Maximum Temperatures on 20 Will Be Slightly Lower

According to the forecast issued at 11 a.m. on August 19, the nationwide daytime high-temperature range is 30–34°C on 19 and 29–33°C on 20.

According to the author's calculation, both the lower and upper ends of the forecast range decrease by 1°C. However, this does not mean that the nationwide average temperature will fall by exactly 1°C. The calculation compares only the two endpoints of the nationwide temperature ranges.

The areas forecast to receive rain and showers will also change. On 19, showers are forecast for southern Gyeonggi, southern Gangwon's inland and mountainous areas, Chungcheong and southern regions. However, southern Gangwon's inland and mountainous areas are excluded from the shower forecast for 20. Jeju Island, meanwhile, has a separate rain forecast extending from early morning through the afternoon.

Because both the precipitation zones and expected rainfall amounts can change from one day to the next, using the weather on 19 to make unchanged plans for 20 could lead to decisions that do not match the actual forecast.

What Should You Check Before Commuting or Going Out?

On August 20, checking your location and the relevant time period first is more practical than relying on a one-line nationwide weather summary.

If you are in southern Gyeonggi, Chungcheong or southern regions, check the likelihood of showers between 9 a.m. and 9 p.m. If you are on Jeju Island, check the rain forecast from early morning through 6 p.m. Even in areas outside the main shower zones, such as Seoul and Gangwon Province, it is worth separately checking the possibility of light morning raindrops and the detailed local forecast.

On days when showers are forecast, it is better to consider the weather throughout your travel period rather than leaving your umbrella behind simply because the morning is clear or dry. If rain begins while driving, visibility may decrease and roads may become slippery, so drivers should reduce speed and maintain a generous distance from the vehicle ahead.

Daytime temperatures could rise to 33°C. If you expect to spend a long time outdoors, bring water and adjust your schedule to avoid prolonged exposure during the hottest hours.

How Will the Weather Change on August 21?

After the showers on 20 end, the areas expecting precipitation will change again. On 21, rain is forecast in parts of the metropolitan area, inland and mountainous Gangwon, and northern South Chungcheong beginning in the evening.

Nationwide temperatures on 21 are expected to range from 20 to 25°C in the morning and from 28 to 33°C during the day. Compared with 20, the upper limit for daytime highs remains 33°C, but the areas and times expecting precipitation will differ.

Anyone planning Friday evening travel or outdoor activities should check the latest short-term forecast for 21 separately rather than applying the shower forecast for 20 unchanged. Precipitation zones and timing may be adjusted as new short-term forecasts are released.

The most important consideration when planning activities on August 20 is not the general statement that 'showers are expected nationwide,' but whether your location falls within southern Gyeonggi, Chungcheong, southern regions or Jeju Island, and whether the expected rainfall overlaps with the time you need to be outside. Even when it is not raining, daytime temperatures may reach 33°C, so it is advisable to prepare for both rain and heat.