Parts of Europe are experiencing a severe heatwave. Several countries are suffering through the second heatwave of the year, leading to dangerous spikes in ground-level ozone pollution with devastating consequences for human and environmental health, warns the European Environmental Bureau (EEB), Europe’s largest network of environmental NGOs.

After several days of temperatures above 35°C, Italian authorities issued a red alert for June 21 in eight cities, including ​Bologna, Florence, Milan, and Turin. France had 49 departments on red heat alert for 22-23 June, while Spain forecast 40-42°C across major inland valleys, locally reaching 44°C. For Belgium, it is serious and likely to intensify rather than yet demonstrably ‘historic.’

The RMI forecast on June 22 calls for 32°C centrally, and 34°C in the south, rising to 33-35°C on Tuesday and locally 37°C on Wednesday-Thursday, with warm nights. Uccle reached 32°C on June 19, a record for that calendar date.

The ⁠spike in temperatures is being driven by a mass of hot air moving north from the Sahara, fuelled by a strong high‑pressure ​system known as the ‘African anticyclone.’

Meteorologists say the system is creating a so‑called ‘heat dome,’ trapping hot air over western and central Europe and ​allowing temperatures to build day after day.

Photochemical smog

Extreme temperatures have serious health repercussions but the impacts of a photochemical smog, which forms as a result of ground-level ozone pollution, remains little known.

In 2022, exposure to ozone pollution, driven largely by methane from industrial agriculture practices, led to an estimated 70,000 premature deaths and €2 billion in crop losses across the EU.

Heatwaves exacerbate the problem, leading to breaches of the alarm level threshold. Luc Powell, Senior Policy Officer for Air Quality and Agriculture at the EEB, warns:  “Once again, dangerous spikes in ground-level ozone pollution, fuelled by heatwaves, are sweeping across the continent.”

“The resulting photochemical smog chokes the air we breathe, damages crops, and places additional pressure on already stressed ecosystems.”

The word smog is a contraction of the English words smoke and fog. In the summer, smog consists mainly of ozone (O3). Ozone is also found high in the atmosphere: there it protects us from harmful UV radiation. But near Earth’s surface (where we live), ozone is unhealthy.

Health repercussions

Heat, sunlight, and stagnant air can sharply increase ground-level ozone. Ozone is formed when pollutants, such as methane, react with nitrogen oxides (NOX) in the presence of sunlight.

While the exact mix of responsible pollutants is complex, the latest report by Ricardo identifies methane as being responsible for 35-37% of harmful ground-level ozone, making it a critical target for air quality improvement.

The health concern is real: ozone, a component of smog, can worsen breathing problems, asthma, and lung function.

Methane is currently excluded from the National Emission Reduction Commitments (NEC) Directive and the Gothenburg Protocol, thereby missing a major opportunity to recognize its role in ozone formation and support efforts to reduce emissions.

Conclusion

Europe is experiencing an exceptionally early, continent-spanning heat episode with severe conditions in France, Iberia, and parts of central Europe. Belgium is entering a high-impact heat spell with daily records and forecasts near 37°. Still, it is premature to call it a nationally historic event until the episode and official observations are complete.

Other damages

The extreme heat has ‌begun to ⁠disrupt infrastructure. In France, SNCF chief Jean Castex said the rail network was “strongly impacted” by high temperatures, and in Berlin, heavy rain disrupted the open‑air Fete de la Musique festival.

Wildlife rescuers are also reporting mounting pressure. A center near the Belgian city of Namur said it had taken in around 150 heat‑stressed animals in recent days, with young birds particularly at risk. Experts say the situation reflects a broader trend: heatwaves in Europe are becoming more frequent and intense due to climate change.