How Does Climate Change Affect Changma Precipitation
Meteorological Characteristics of the Korean Peninsula Changma
Average length and start date
The Changma typically lasts between 3 and 5 weeks, with the average duration being around 31 to 32 days (about a month). It usually starts near June 24 and June 25 in the order of Jeju, southern and central regions.
The selection of 3 different Chanma periods (2015, 2019, 2020) and their individual periods
(Seo and Choi, 2022)
Average Rainfall volume
During Changma, South Korea typically receives approximately 30~35% of its annual rainfall. The average number of rainy days is approximately 17 to 18 per region and the average rainfall during this period is between 340~ 380mm across the main regions of South Korea.
Seoul Monthly Average Precipitation (KMA)
This Diagram highlights the heavy rainfall in summer, with July and August showing the highest precipitation of the year due to the monsoon season
Rainfall pattern
Rainfall often occurs in heavy, sustained bursts, sometimes lasting for days which can lead to flooding (more than 80 mm day−1), with intense thunderstorms.
The consistent supply of moisture from the south via a low level jet stream fuels the prolonged precipitation along the stationary front.
Spatial distribution of the frequency of daily rainfall of more than (a) 80 mm (heavy) and (b) 150 mm (extreme) recorded at the weather stations during the two rainy seasons from 1976 to 2023. The size and colour of the circles represent the frequency. (Ho et al.,2025)
High Humidity
The warm moist air mass from the pacific leads to a dramatic increase in absolute and relative humidity, often making the weather feel sticky and uncomfortable, and contributing to mold and dampness issues.
Seoul's humidity levels vary throughout the year. The highest levels occur in July, reaching 77% (high), while the lowest is recorded in February at 54%.