Meteorologists have declared smog situations in Prague, the Central Bohemian region, and the Ústí nad Labem region due to dangerously high concentrations of ground-level ozone, with alerts effective from Tuesday afternoon until further notice. The smog situation in Ústí nad Labem marks the third such declaration in the region since late June.
The alerts coincide with a fresh heatwave gripping the Czech Republic since Monday, with maximum temperatures reaching 34 to 39 degrees Celsius and perceived temperatures commonly approaching 50 degrees. Ground-level ozone forms when hydrocarbons and nitrogen oxides react under intense sunlight. The Czech Hydrometeorological Institute has advised the public to limit strenuous outdoor activity during afternoon hours, particularly for those with chronic respiratory conditions, the elderly, and young children. Elevated ozone exposure can cause burning eyes, coughing, headaches, and chest tightness.
Separate warnings for extreme heat, thunderstorms, and fire risk remain in force nationwide. Smog situations were also declared last week across five Czech regions before being lifted ahead of the weekend.