South Korea is preparing for a period of extreme humid heat and sudden heavy rainfall through late July and early August [1, 2].

This weather pattern creates a significant public health risk as the combination of high temperatures and extreme moisture increases the likelihood of heat-related illnesses. The volatility of the forecast, which includes potential typhoon activity, further complicates emergency preparations for inland regions and coastal areas like Jeju Island [1, 2].

Forecasters describe the upcoming period as an "ultra-humid" heat spell. This condition is driven by a hot high-pressure system sitting over the Korean Peninsula combined with a massive influx of tropical moisture moving in from the south [1, 2].

Lee Jae-jung, a forecast team leader at KWeather, said typical daytime temperatures are expected to reach 33°C [1]. However, the heat will persist well into the night. Reporter Jung Hye-yoon said nighttime low temperatures will fluctuate around 30°C [1], leading to severe "ultra-tropical nights" where temperatures do not drop sufficiently for recovery from the day's heat.

Beyond the heat, meteorologists are monitoring the possibility of a north-moving typhoon [1, 2]. Such a system would introduce further instability to the region's weather, potentially triggering sudden and intense bursts of heavy rain. This variability follows the conclusion of the traditional monsoon season, shifting the focus from steady seasonal rain to more erratic, moisture-heavy events [1, 2].

Local authorities are advising residents to monitor weather updates closely as the interaction between the high-pressure system and tropical moisture creates an unpredictable environment. The combination of extreme humidity and high heat can make the perceived temperature feel significantly higher than the actual thermometer reading [1, 2].

“Nighttime low temperatures will fluctuate around 30°C”

The shift toward 'ultra-humid' heat represents a transition from typical summer warmth to a more oppressive atmospheric state. When high humidity prevents sweat from evaporating, the body cannot cool itself effectively, increasing the risk of heatstroke even at moderate temperatures. The addition of a potential typhoon suggests that the region will face a dual threat of extreme thermal stress and flash flooding during this window.