A child splashes in the water of a fountain in Gwanghwamun Square in central Seoul, Friday. Yonhap

This June has seen a record number of heat wave days, surpassing even the infamous heat of 2018, previously considered the highest on record. While the onset of the monsoon season will abate the early heat wave temporarily, even more intense heat is expected in July and August.

According to data from the Korea Meteorological Administration (KMA), the number of heat wave days from June 1 to 20 this year was 2.4, already quadrupling the average for the month between 1991 and 2020. During the record-breaking summer in 2018, it recorded 1.5 heat wave days.

Heat wave days are defined as when the daily maximum temperature reaches 33 degrees Celsius or higher.

In 2018, the heat wave intensified after a brief monsoon season, with July and August recording 15.4 and 14.1 heat wave days, respectively.

The summer of 1994, previously the second-highest record for heat waves, saw 0.9 days in June, 17.7 days in July and 9.8 days in August. The heat extended to September, recording 1.2 heat wave days.

The KMA attributes this year's early heat wave to a migratory anticyclone resulting in clear skies and increased solar radiation. Additionally, warm and humid southwesterly winds contributed to the rising temperatures.

The early summer heat wave is expected to subside temporarily with the onset of the monsoon season. The monsoon began in Jeju on Wednesday and extended to the southern part of the country on Sunday.

The KMA forecasts that next week's temperatures will range from 18 to 24 degrees Celsius in the mornings and 25 to 31 degrees during the day. These temperatures are expected to be similar to or slightly above the average, which typically sees lows of 18 to 21 degrees and highs of 25 to 29 degrees.

However, following the monsoon season, an even more intense heat wave is anticipated, surpassing the heat wave experienced in June.

Korea's summers typically heat up in June, slow during the rainy season and then peak with a full-fledged heat wave from July to August. It is predicted that this early summer heat wave is just the beginning of a particularly hot season this year.

In addition, while June's heat is characterized as a dry heat due to a migratory anticyclone, July and August are expected to feel like a sauna because of the hot and humid air brought by the North Pacific anticyclone.

According to the KMA's long-term forecast, there is a 50 percent chance that the average temperatures will exceed the norm in June and August this year. For July, there is a 40 percent chance that temperatures will be similar to or higher than the average.

People with umbrellas walk at a street in Myeong-dong in Seoul, Saturday. Yonhap

Meanwhile, a recent forecast indicates that escalating levels of greenhouse gases are intensifying the heat wave conditions. The KMA projects that the number of heat wave days in Seoul could soar to nearly 110 days by the second half of the 21st century.

By utilizing climate change models and greenhouse gas data, the KMA is assessing potential scenarios across 17 cities and provinces.

Without significant reductions in emissions, a scenario suggests an alarming rise in heat waves. Specifically, from 2081 to 2100, Seoul could experience an average of 109.8 heat wave days, compared to the current average of 11.3.

Furthermore, the city's nighttime temperatures are anticipated to transform drastically, with tropical nights increasing to an average of 96.1 days during the same period, marking an 8.5 times rise from the current 11.3 days.

The average annual precipitation in Seoul is also anticipated to rise by 252.3 millimeters to 1,521.9 millimeters, up from the current 1,269.6 millimeters.

KWeather, a private meteorological company, expressed concerns about the rapid degradation of Korea's climate, which is changing since last year at a faster pace than many organizations predicted.

As of 2022, Korea has become the world's 13th-largest emitter of greenhouse gases. It highlighted the critical need for comprehensive actions to reduce carbon dioxide emissions, such as expanding renewable energy sources, increasing planting trees.