Korea has a temperate climate characterized by four distinct seasons. The seasons change gradually but each has a significant seasonal characteristic. Spring and autumn are relatively short while summer and winter are rather long. With high temperature and humidity, summer begins in June and lasts until August accompanied with monsoon typhoons and rains. Winter is dry and cold due to the northwesterly winds sweeping down from Siberia. An annual average temperature is 12~14˚C in the central region and 3~20˚C in the northern region.
Annual mean rainfall ranges from 600mm to 1,800mm with uneven seasonal distribution and regional differences : 1,000mm to 1,800 mm in southern region ; 1,100 mm to 1,400 mm in central region. The rainy season begins in late June and lasts approximately 30 days, and two or three typhoons from the northern Pacific Ocean affect Korea between June and October every year. 50~60% of the annual rainfall is likely concentrated during summer causing great concerns for unstable water supply.