The climate of Seoul features a humid subtropical and humid continental climate (Köppen climate classification). Seoul is classed as having a temperate climate with four distinct seasons, but temperature differences between the hottest part of summer and the depths of winter are extreme. In summer the influence of the North Pacific high-pressure system brings hot, humid weather with temperatures soaring as high as 35 °C (95 °F) on occasion. In winter the city is topographically influenced by expanding Siberian high-pressure zones and prevailing west winds, temperatures dropping as low as -13.7 °C (7 °F). The bitterly cold days tend to come in three-day cycles regulated by rising and falling pressure systems, during winter snowfall can cause frosty weather in the city. The most pleasant seasons in the city are spring and autumn, when azure blue skies and comfortable temperatures are a sure bet. The city experiences heavy rainfall almost every month, but most of it falls in the summer monsoon period between June and September, as a part of East Asian monsoon season.[1]
| Climate data for Seoul (1981−2010) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average high °C (°F) | 1.5 (34.7) |
4.7 (40.5) |
10.4 (50.7) |
17.8 (64.0) |
23.0 (73.4) |
27.1 (80.8) |
28.6 (83.5) |
29.6 (85.3) |
25.8 (78.4) |
19.8 (67.6) |
11.6 (52.9) |
4.3 (39.7) |
17.0 (62.6) |
| Daily mean °C (°F) | −2.4 (27.7) |
0.4 (32.7) |
5.7 (42.3) |
12.5 (54.5) |
17.8 (64.0) |
22.2 (72.0) |
24.9 (76.8) |
25.7 (78.3) |
21.2 (70.2) |
14.8 (58.6) |
7.2 (45.0) |
0.4 (32.7) |
12.5 (54.5) |
| Average low °C (°F) | −5.9 (21.4) |
−3.4 (25.9) |
1.6 (34.9) |
7.8 (46.0) |
13.2 (55.8) |
18.2 (64.8) |
21.9 (71.4) |
22.4 (72.3) |
17.2 (63.0) |
10.3 (50.5) |
3.2 (37.8) |
−3.2 (26.2) |
8.6 (47.5) |
| Precipitation mm (inches) | 20.8 (0.819) |
25.0 (0.984) |
47.2 (1.858) |
64.5 (2.539) |
105.9 (4.169) |
133.2 (5.244) |
394.7 (15.539) |
364.2 (14.339) |
169.3 (6.665) |
51.8 (2.039) |
52.5 (2.067) |
21.5 (0.846) |
1,450.5 (57.106) |
| % humidity | 59.8 | 57.9 | 57.8 | 56.2 | 62.7 | 68.1 | 78.3 | 75.6 | 69.2 | 64.0 | 62.0 | 60.6 | 64.4 |
| Avg. precipitation days (≥ 0.1 mm) | 6.5 | 5.8 | 7.4 | 7.8 | 9.0 | 9.9 | 16.3 | 14.6 | 9.1 | 6.3 | 8.7 | 7.4 | 108.8 |
| Sunshine hours | 160.3 | 163.3 | 189.0 | 205.0 | 213.0 | 182.0 | 120.0 | 152.5 | 176.2 | 198.8 | 153.2 | 152.6 | 2,066.0 |
| Source: Korea Meteorological Administration [2] | |||||||||||||
Contents |
Seoul has a wet climate almost all year round especially during the summer season, with cold and chilly weather during the winter season. Winters are usually long, cold, and dry, whereas summers are short, hot, and humid. Spring and autumn are pleasant but short in duration, spring and autumn are considered the best time to visit Seoul.[3]
Like all temperate climates in the world, Seoul also has four seasons: winter, summer, autumn and spring. The monsoon season and typhoons also occurs in the summer season.[5]
The winter in Seoul is controlled by the large Siberian high pressure system (the Asiatic high), which results in predominantly cold, dry north-westerly winds. About every 4 to 5 days a low-pressure trough will move through South Korea, bringing with it cloudiness and light precipitation. The amount of precipitation locally depends mostly on the elevation of the station and the length of time that the air has been over the Yellow Sea. Maximum snowfall occurs over the northwest coast, which is the most exposed to the northwesterly flow, and in the mountain areas. Normally less than 10 percent of the annual precipitation falls during the winter. Frequently the weather is cloudless, clear, and dry, except for the southwestern region of the peninsula. The mean January temperature in Seoul is -4.4 °C (24 °F). January is the coldest month in Seoul.
April marks the start of the transition from the cold, dry winter to the summer rainy season. This transition lasts nearly 2 months. Low pressure systems start forming near the Gulf of Bo Hai and the Shantung Peninsula. These lows significantly erode the dominance of the Siberian High (Asiatic High) pressure system. As a result, cloudiness and precipitation increase during the spring months. Korea is occasionally influenced by the Yellow Wind during the spring months. The Yellow Wind occurs when storm winds behind a trough cause dust from the Gobi Desert to become suspended in the air. The dust laden air is subsequently transported over Korea. During a strong yellow wind, visibility can be reduced to less than 1 mile. Spring is also the time for heavy sea fog to form over the coastal areas. The fog forms as the warmer air passes over the cooler Yellow Sea and the Sea of Japan (East Sea). Wind gusts of up to 59 kts have been recorded as well as tornados. The average April temperature in the north is approximately 10 °C (50 °F) and in the south 12 °C (54 °F); spring is generally cooler than fall.
Summer is the rainy season in Seoul. During the summer, East Asian monsoon winds engulf the city and the warm, moisture laden air moving off the oceans clashes with the drier air to the north. These fronts oscillate back and forth across Korea during the summer months. The interior highlands disturb the winds, forcing them into a westerly/southwesterly direction. The majority of the annual precipitation falls between late June and the middle of September, with rains fully developing along the entire peninsula by mid-June. Seoul receives approximately 126 mm (5 in) of precipitation during the winter (December–March), but in July alone receives approximately 383 mm (14.3 in). July is the wettest month in the metropolis.
Thunderstorms usually occur about 2 to 5 days per month during this period. Summer precipitation in Seoul is as likely to occur at 0200 as at 1400. Humidity is very high and fog will develop whenever a cold air mass confronts this moisture laden air, often forming on cloudless days. The typhoon season occurs from July through September. About once each year, a typhoon will pass very close to or move over Korea, causing heavy showers. Strong winds are usually confined to islands and exposed coastal areas. Although winds might not pose a problem, the associated rainfall can cause significant flash flooding, a very real threat during the rainy season, especially in rough terrain. The mean temperature for Seoul in August is 25.3 °C (78 °F)
October is the transition month between the summer rainy season and the cold, dry winter. The predominantly tropical cloudy weather of the summer is replaced by cooler, drier, and less cloudy conditions. The primary weather producers during October are cold frontal systems from the Asian mainland. On the average, one frontal passage per week can be expected during the month. A typical frontal passage is preceded by increasing middle and high cloudiness with light rain. Following the frontal passage, mostly clear skies can be expected for 3 or 4 days. During this clear period it is very likely for fog to form. Fog is especially prevalent in river valleys and in low lying areas.