Geography of Korea: I. Natural Environment > 3. Climate > 2) Temperatures
(1) Annual Mean Temperatures
Affected by the northwest monsoon, the Korean Peninsula has severe winters and so its annual mean temperature is lower than in other regions that share its latitude. The highest average temperature in Korea is 16.6˚C at Seogwipo on Jeju Island. On the Korean mainland, average temperatures are highest in the southeastern coastal region—Changwon is at 14.9˚C, Busan and Tongyeong at 14.7˚C. The lowest annual mean temperature in South Korea is 6.6˚C at Daegwallyeong, while in North Korea it is 0.2˚C at Samjiyeon on the Kaema (Gaema) Plateau.Generally average temperatures drop as one ascends in altitude and so an isothermal temperature chart of the world will show average temperature values changing as one moves from sea level towards higher altitudes. However, an isothermal chart of the Korean Peninsula does not exhibit such a pattern, rather measurements are taken.
Looking more closely at mean annual temperatures, for Jeju Island, Seogwipo (16.6˚C), Jeju city (15.8˚C), Gosan (15.6˚C), and Seongsan (15.4˚C), bringing the average mean temperature for Jeju Island as w hole to just over 15˚C (Image 1-6). Besides Jeju, other areas with mean annual temperatures above 13˚C include Tongyeong (14.7˚C), Geoje (14.2˚C), Busan (14.7˚C), Jinju (13.1˚C), Changwon (14.7˚C), Miryang (13.3˚C), Ulsan (14.1˚C), Daegu (14.1˚C), Pohang (14.2˚C), Gangneung (13.1˚C), Yeosu (14.3˚C), Mokpo (13.9˚C), Gwangju (13.8˚C), Jeongeup (13.1˚C), Jeonju (13.3˚C), and Daejeon (13.0˚C), all predominantly in the regions of Yeongnam (i.e., Gyeongsangnam-do and Gyeongsangbuk-do provinces) and Honam (i.e., Jeollanam-do and Jeollabuk-do provinces).
Areas with mean annual temperatures above 11˚C are generally located in the central region of Korea and include Yeongcheon (12.4˚C), Gumi (12.5˚C), Andong (11.9˚C), Mungyeong (11.8˚C), Yeongju (11.3˚C), Wonju (11.3˚C), Chuncheon (11.1˚C), Sokcho (12.2˚C), Namwon (12.3˚C), Gunsan (12.8˚C), Boryeong (12.4˚C), Cheongju (12.5˚C), Seosan (11.9˚C), Cheonan (11.8˚C), Chungju (11.2˚C), Icheon (11.6˚C), Suwon (12.0˚C), Incheon (12.1˚C), and the capital of Seoul (12.5˚C). Areas with annual mean temperatures below 11˚C are generally limited to mountainous areas and include Jangsu (10.5˚C), Boeun (10.9˚C), Bonghwa (9.9˚C), Jecheon (10.2˚C), Taebaek (8.7˚C), Hongcheon (10.3˚C), Daegwallyeong (6.6˚C), and Cheorwon (10.2˚C).
(2) Winter Temperatures
From the start of the Korean winter in November temperatures drop precipitously as a result of the development of high pressure systems in Siberia that brings on the northwest monsoons. The mean temperature on the Kaema Plateau in North Korea for the month of November is -4˚C, and by December this has dropped to -14˚C. In December the mean temperature dips below freezing as far south as the central regions of the peninsula.
By the peninsula’s coldest month of January, with the exception of Jeju Island and the southern coastal region, mean temperatures Korea-wide have fallen below freezing. In January, the southern interior and the central regions have mean temperatures of between 0˚C and -5˚C, while in Huchang, Jangseong, and Ganggye in Pyeonganbuk-do province, as well as in Samsu and Gapsan on the Kaema Plateau, the mean temperature for January is about -18˚C. The highest mean temperature for January is in Seogwipo on Jeju Island (6.8˚C), while the lowest is in Jungjangjin in Pyeonganbuk-do province in North Korea (-20.8˚C). Thus, the temperature difference between north and south can surpass 25˚C.
Regarding mean January temperatures, a look at a isothermal map would reveal a significant southward dip of the isothermal lines in the southern interior regions, indicative of the pronounced temperature differences between the inland and coastal areas. Further, comparing the January mean temperatures between the eastern and western coastal regions, we find that Gangneung on the east coast is at 0.4˚C and Incheon on the west is -2.1˚C, while Hongcheon and Cheorwon on the interior mean temperatures dip as low as -5.5˚C. The reason for the higher January mean temperatures on the east coast compared to the west coast is the fact that the Taebaeksanmaek mountain range acts as a screen blocking the frigid northwest monsoon winds and the resulting Foehn phenomenon that sometimes occurs. The water temperature in the East Sea is also slightly warmer than that of the Yellow Sea in the west.
In February, the “Siberian High” high-pressure system shrinks and so temperatures rise somewhat, yet the isothermal lines remain fairly unchanged from January. Mean temperatures for February include, Seogwipo (7.8˚C), Gangneung (2.2˚C), Incheon (0.3˚C), and Hongcheon and Cheorwon (-2.3˚C). In March temperatures on the peninsula rise markedly as spring makes its definitive entrance.
The lowest temperature ever recorded on the Korean Peninsula was -43.6˚C at Junggangjin, in present-day North Korea on the Chinese border, on January 12, 1933. The lowest recorded temperature for South Korea is -32.6˚C, recorded at Yangpyeong in Gyeonggi-do province on January 5, 1981, followed by -29.2 at Cheorwon (January 16, 2001), -28.9˚C at Daegwallyeong (January 24, 1974), -28.5˚C at Chungju (January 5, 1981), -28.1˚C at Hongcheon (January 5, 1981), -27.9˚C at Chuncheon (February 6, 1969), -27.6˚C at Wonju (January 5, 1981), and -27.4˚C at Jecheon (January 4, 1981).
(3) Summer Temperatures
Summer arrives in June and with the sun now higher in the sky the days grow longer and temperatures gradually rise. Mean temperatures in June range from 14–18˚C on the Kaema Plateau in North Korea to 20–22˚C elsewhere on the peninsula. By July, with the exception of the Kaema Plateau, temperatures peninsula-wide reach around 25˚C as the summer heat wave begins in earnest.
With the end of the summer rainy season (jangma) in August the peninsula comes under the influence of North Pacific high-pressure systems, with most areas experiences their hottest temperatures of the year. During this time almost all areas south of a line between the North Korean cities of Sinuiju in the west and Hamheung in the east experience mean temperatures of between 24˚C and 26˚C, with the exception of the area around Mt. Taebaek, which has a cooler mean average of 21˚C.
In areas to the north of the aforementioned line temperatures are higher in July than August. For July, the Kaema Plateau and adjacent areas experience highs between 18˚C and 20˚C, while the mountainous region of Pyeonganbuk-do province experiences July highs of 22˚C–24˚C, surpassing its August averages. The highest average high occurs on Seogwipo on Jeju Island—27.1˚C during the hottest month of August. Compared to the lowest average high of 18.7˚C in Pungsan in July, we can note an average high temperature difference of over 9˚C.
The highest temperature recorded on the Korean Peninsula was 40˚C at Daegu on August 1, 1940. Other record highs in South Korea include 39.8˚C at Chupungnyeong (August 21, 1939), 39.4˚C at Miryang (July 20, 1994), 39.4˚C at Yeongcheon (July 20, 1994), 39.4˚C at Gangneung (July 25, 1942), 39.3˚C at Sancheong (July 20, 1994), 39.2˚C at Gimhae (August 10, 2013), 39.2˚C at Hapcheon (July 20, 1994), and 39˚C at Changwon (July 20, 1994).
(4) Annual Temperature Ranges
In Korea, the mean temperature ranges between the hottest and coldest months, what is termed the annual temperature range, becomes more pronounced as you both move south to north and from coast to interior. The smallest annual temperature range is at Gosan on Jeju Island, where on average only 20˚C separates the hottest from coldest days, while the greatest annual range is 43.5˚C at Junggangjin in North Korea on the border with China. In Seoul, the annual temperature range is 28.1˚C. The annual temperature range of the West Coast city of San Francisco in the United States, though it sits at roughly the same latitude as Seoul, is only 8.5˚C. And London, which actually occupies a much higher latitude than Seoul, experiences an average temperature range of only 13.4˚C. This illustrates the differences between weather on eastern and western coasts.