Part of the East Asian monsoonal region, South Korea has a temperate climate with four distinct seasons. The movement of air masses from the Asian continent exerts greater influence on South Korea's weather than does air movement from the Pacific Ocean. Winters are usually long, cold, and dry, whereas summers are short, hot, and humid. Spring and autumn are pleasant but short in duration. Seoul's mean temperature in January is -5° C to - 2.5° C; in July the mean temperature is about 22.5° C to 25° C. Because of its southern and seagirt location, Cheju Island has warmer and milder weather than other parts of South Korea. Mean temperatures on Cheju range from 2.5° C in January to 25° C in July.

The country generally has sufficient rainfall to sustain its agriculture. Rarely does less than 75 centimeters of rain fall in any given year; for the most part, rainfall is over 100 centimeters. Amounts of precipitation, however, can vary from year to year. Serious droughts occur about once every eight years, especially in the rice-producing southwestern part of the country. About two-thirds of the annual precipitation occurs between June and September.

South Korea is less vulnerable to typhoons than Japan, Taiwan, the east coast of China, or the Philippines. From one to three typhoons can be expected per year. Typhoons usually pass over South Korea in late summer, especially in August, and bring torrential rains. Flooding occasionally causes considerable damage. In September 1984, record floods caused the deaths of 190 people and left 200,000 homeless. This disaster prompted the North Korean government to make an unprecedented offer of humanitarian aid in the form of rice, medicine, clothes, and building materials. South Korea accepted these items and distributed them to flood victims.

Data as of 1990