Weather in Seoul

On this site the months that score closest to a 22°C day, lighter rain, and moderate humidity are June, July, and September. Seoul is in South Korea at 37.6°N. The 2001–2020 NASA POWER daily record describes a continental climate with a wide temperature swing.

August is the warmest month (average 25.0°C, high 28.3°C) and January is the coolest (average -3.1°C, low -6.9°C). Rain is wet season runs from June to September, inside an annual total of 1240 mm. The wettest month is July at 361 mm; the driest is January at 20 mm.

Best months to visit Seoul

The three months with the highest comfort score are June, July, and September: June (21.0°C average, 116 mm, 76% humidity); July (24.2°C average, 361 mm, 85% humidity); September (20.5°C average, 138 mm, 79% humidity). They fall in calendar order. The score rewards averages near 22°C, lower rainfall, and humidity near 60%. It is a climate score, not a festival or price calendar.

If you want the wet season itself — fewer crowds, greener landscape, heavier rain — aim at June–September instead of the score.

Hot and cool months in Seoul

The heat peaks in August, when the typical afternoon is 28.3°C. The opposite pole is January, when mornings average -6.9°C.

Mean high across all twelve months is 15.6°C and mean low is 7.2°C. These are 20-year grid averages, so a city station can read a few degrees warmer or cooler.

When Seoul gets wet

The wet season in Seoul starts in June and ends in September (June, July, August, and September). July is the core of it at 361 mm. January is the other extreme, with 20 mm.

A rainy day here is a day with at least 1 mm in the NASA POWER series. July averages 18 such days; January averages 4.

The calendar in Seoul

January is the coolest month, with lows around -6.9°C and highs near 0.6°C. Rainfall is 20 mm. February brings 31 mm and 4 rainy days; temperatures run from -4.7°C to 3.4°C. March stands apart from the months beside it: 8.9°C / -0.8°C and 37 mm. April: 15.3°C high, 4.7°C low, 72 mm rain, 74% humidity. In May, Seoul averages 21.3°C by day and 10.8°C at night, with 84 mm of rain. The wet season opens in June. Expect 116 mm and 10 rainy days, with nights around 16.5°C.

July is the wettest month — 361 mm and 18 rainy days, with 85% humidity. Peak heat arrives in August: 28.3°C by day, 21.7°C at night, and 83% humidity. September closes the wet season: 138 mm over 10 rainy days, then the calendar dries. In October, Seoul averages 18.5°C by day and 9.6°C at night, with 54 mm of rain. November: 10.7°C high, 2.7°C low, 47 mm rain, 76% humidity. December stands apart from the months beside it: 2.7°C / -4.4°C and 22 mm.

How Seoul compares inside South Korea

Daejeon is about 140 km away: Seoul is about as warm as Daejeon at the hot peak and a similar annual rainfall (1225 mm in Daejeon). Daejeon’s wettest month is July (316 mm) versus July here.

Daegu is about 237 km away: Seoul is about as warm as Daegu at the hot peak and a similar annual rainfall (1201 mm in Daegu). Daegu’s wettest month is July (264 mm) versus July here.

Gwangju is about 268 km away: Seoul is about as warm as Gwangju at the hot peak and 141 mm drier over the year than Gwangju. Gwangju’s wettest month is July (290 mm) versus July here.