Heavy rain is increasingly striking South Korea during early-morning commuting hours due to specific nighttime atmospheric patterns [1, 2].
These "extreme dawn downpours" create significant hazards for millions of workers traveling during the first hours of the day. The timing of these weather events complicates urban transit and increases the risk of flash flooding during peak traffic periods.
Professor Lee Hyun-ho of Kongju National University's Department of Atmospheric Science said that these events are effectively "nocturnal heavy rains" [1, 2]. According to Lee, the phenomenon occurs because low-pressure centers frequently pass through the region at night while moisture levels remain high [1, 2].
Lee said that the behavior of the air changes significantly between day and night. During the day, air moves actively and mixes well from the ground up to the upper atmosphere [1, 2]. However, at night, a thin layer of stable air forms near the surface [1, 2].
This stable air layer reduces wind shear, which allows heavy rain to develop and intensify more easily than during the day [1, 2]. The combination of high moisture and low wind interference creates an environment where rainfall can rapidly escalate into what residents describe as "water bombs" [1, 2].
Anchor Lee Sena said that recent patterns show a trend of heavy rain pouring down during late nights, early mornings, and specifically during the morning commute [1, 2]. The convergence of these meteorological factors ensures that the most intense precipitation often coincides with the highest volume of commuters on the road [1, 2].
“"It is a nocturnal heavy rain that falls particularly heavily at night."”
The shift toward nocturnal and early-morning precipitation peaks suggests that traditional daytime weather forecasting may not sufficiently warn commuters of sudden, intense rainfall. As stable air layers and moisture levels synchronize during the dawn hours, urban infrastructure in South Korea may face increased pressure to manage flash-flood risks during the most vulnerable transit windows of the day.
