South Korea in recent years has seen a significant rise in both the number of days with midday temperatures of 33 degrees Celsius and above, and the number of "tropical nights," where temperatures remain at or above 25 C throughout the night.

To avoid any confusion, the climate of the Korean Peninsula is categorized as temperate, not tropical. Nevertheless, meteorological authorities and people in South Korea and Japan tend to label their sweltering summer nights as "tropical." This designation arises from the combination of high humidity and nighttime temperatures, resulting in a weather reminiscent of tropical regions.

Sleepless nights in Seoul

Meteorologists say tropical nights are a phenomenon more commonly observed in big cities in South Korea, where the dense and compact urban layout of structures effectively traps heat.

For Seoul, the number of tropical nights have increased significantly in the past decade. From 1908 to 2011, the number of tropical nights in Seoul rose above 20 only once -- in 1994, when it recorded a whopping 36 hot nights.

But since 2012, there were six years with 20 or more tropical nights. Between 2012 and 2022, the average number of tropical nights per year was 19.6.

This contrasts with the 1991-2020 average of 12.5. While 20 days would have been an outlier in the 2000s or 1990s, it was just slightly above average in the 2010s.

The number of days with midday temperatures of 33 C or higher rose similarly in the same period. The number of such hot days surpassed the 15-day mark only twice in the 20th century -- 29 days in 1994 and 16 in 1997 -- but since 2012, there were six years with 15 days with peak temperatures of 33 C or above.

This year, while it is still mid-August, the capital city had 16 days with 33 C or above temperatures as of Tuesday, along with 18 tropical nights -- strong indications that the 2023 will also be a stuffy year.

Chilling nights in Taebaek

Stats suggest that Taebaek in mountainous Gangwon Province may be the coolest city in the country. So far this year, the temperature in Taebaek reached 33 degrees Celsius or above for only one day. The city had only 33 days with such a high temperature since 2013, 16 of which were in 2018 -- widely referred to as one of the hottest summers in recorded history.

The very first time the midday weather for Taebaek city reached 33 C was in 2005, and it happened only for 40 days in the city, since data began.

The number of tropical nights in the city’s history was four, in stark contrast to the 197 days in Gangneung in the same province in just the past four years.

Gangneung is among the exceptions in the region, with it already recording 18 days with 33 C or above and 22 tropical nights this year.

The average temperature for Taebaek from June and August in the past 10 years was 22.2 degrees Celsius, showing that the city at 900 meters above ground level has the coolest place to be amid the blazing heat of this summer.