Home > National > Environment

Caution advised as ozone concentrations surge, sudden showers expected

Published: 28 May. 2025, 14:14 Updated: 28 May. 2025, 18:41

People seek shade at the Han River Park in Yeouido, western Seoul, on May 27. [NEWS1]

Brace for a breath of foul air — and a splash of chaos.

Ozone concentrations are forecast to surge to “very bad” levels on Wednesday and Thursday, worsening air quality nationwide. The volatile weather is also expected to bring sporadic, heavy showers nationwide, prompting caution for those heading outdoors.

The National Institute of Environmental Research’s air quality forecasting center said Wednesday that ozone levels will remain high from early morning to night in all regions, citing influences from foreign air pollutants. Most areas are expected to experience “bad” ozone levels over the two days, while Seoul may reach “very bad,” the highest level on the scale.

Under “very bad” conditions, even healthy individuals are advised to limit outdoor activities and stay indoors, in addition to vulnerable groups such as the elderly and children.

Ozone is formed when air pollutants from vehicles and other sources undergo photochemical reactions under ultraviolet light. These reactions are most active during summer afternoons with intense sunlight and weak wind — conditions that promote ozone buildup.

Unlike fine dust, ozone is invisible and has earned the nickname the “silent killer.” High concentrations can irritate the respiratory system and eyes, and in severe cases, impair lung function or worsen cardiovascular conditions.

While fine dust levels tend to drop during the summer, ozone concentrations typically rise. On Tuesday, Seoul issued its first ozone advisory of the year.

Rising temperatures and solar radiation due to climate change are contributing to an increase in high-ozone days. According to the Ministry of Environment, the number of ozone advisories issued jumped from 46 in 2020 to 81 last year.

“Children, the elderly and people with respiratory or heart conditions should avoid outdoor activities on high ozone days,” the center advised.

People wear umbrellas in the rain in Jung District, central Seoul, on May 16. [NEWS1]

Heavy showers are also forecast.

“As daytime temperatures rise, unstable atmospheric conditions will cause sudden showers of around 10 millimeters [0.4 inches] per hour, accompanied by gusts, thunder and lightning,” the Korea Meteorological Administration (KMA) said Wednesday.

Inland areas may also see hail due to strong upward air currents inside clouds. Sudden rain showers are expected from the afternoon through the evening in Seoul and surrounding areas, including Gangwon, Chungcheong, eastern Jeolla, and Gyeongsang regions.

“The downpours will be highly localized, leading to large differences in rainfall even within the same area,” said a KMA official. “Drivers should be particularly careful, as visibility may decrease and roads may become slippery in affected areas.”

Similar conditions are expected on Thursday, especially in eastern regions from the afternoon to evening. Temperatures will remain cool in the morning but rise sharply during the day, with a daily temperature range of around 15 degrees Celsius [59 degrees Fahrenheit]. Authorities advised the public to monitor their health closely amid the wide temperature swings.

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.
BY CHON KWON-PIL [[email protected]]