Despite its small size Korea experiences a wide range of weather conditions through four distinct seasons—a fact that is boasted on post cards and just about every write-up about Korea. (I once tried to explain to students that many places around the world have four seasons but they looked at me like I was crazy so I let it be.)
The Korean peninsula’s climate is comparable to that of the northeast United States between the same latitudes. Because of the maritime Pacific High, summers are usually hot and humid. At the other extreme, winters in Korea are very cold, influenced by the massive arctic Siberian High sitting north of Mongolia. In between, Korea ‘s spring and autumn are sunny and generally dry. Although a handful of typhoons occur in the western Pacific from June to September, only two or three usually approach the Korean peninsula.
Korea gets plenty of sunshine—a higher percentage than Japan but a little less than the comparative latitudes in the United States. The variation of annual mean temperature ranges from 40 to 61°F (10 to 16°C), except in the mountains.
Korea’s average annual rainfall ranges between 31.5 to 59.1 in (800 and 1,500 mm), about twice that of mainland China and half the amount usually measured in Japan . The peninsula receives over half its total rainfall between June and August—considered the rainy season, and less than 10% of its total precipitation during the dry season, which lasts from October to March.
In my opinion, the worst weather (or rather pollution) phenomenon in Korea is yellow dust. Asian Dust (also yellow dust, yellow sand, yellow wind, or China dust storms) is a seasonal meteorological phenomenon which affects much of East Asia sporadically during the springtime months. The dust originates in the deserts of Mongolia and northern China and Kazakhstan where high-speed surface winds and intense dust storms kick up dense clouds of fine, dry soil particles. These clouds are then carried eastward by prevailing winds and pass over China, North and South Korea, and Japan, as well as parts of the Russian Far East. Sometimes, the airborne particulates are carried much further, in significant concentrations which affect air quality as far east as the United States.
In the last decade or so, it has become a serious problem due to the increase of industrial pollutants contained in the dust and intensified desertification in China causing longer and more frequent occurrences, as well as in the last few decades when the Aral Sea of Kazakhstan started drying up due to a failed Soviet agricultural scheme.
The Korea Times has reported it costing 3 million won, 6000 gallons of water, and 6 hours to simply clean one jumbo jet. Across Korea in the spring, especially on the yellow dust days, it’s a good idea to wear a face mask—available at every corner market in Korea.