By the time France's fourth heatwave of the summer settled over western Europe, more than 330,000 people had already abandoned their homes, and the country had surpassed its worst-ever annual figure for total area burned — with August, historically the most dangerous month, still to come. In Spain, the cumulative number of fires this year has set a new record for this point in the calendar, and the total burnt area is approaching the devastating levels last seen in July 2022. Toxic smoke from both countries has drifted across the continent, and scientists have begun describing the successive blazes as "firewaves." The underlying cause is what climate researchers call "whiplash" weather.

Last winter and much of spring delivered exceptionally heavy rainfall across western Europe — Spain recorded 241% of its normal average precipitation in February 2026 — which encouraged dense growth of trees, shrubs and ground vegetation. Then, from May onwards, a sequence of heatwaves struck. June's event was the most severe ever measured on the continent, producing an average surface air temperature anomaly of 3.06°C for western Europe.

It was, according to scientists, a heat event that would have been impossible without more than a century of accumulated carbon pollution from fossil fuels. The conditions that followed — extreme drought — were estimated to be 80 times more likely as a result of global heating. Dry vegetation became fuel almost overnight. The crisis has been deepened further by a phenomenon previously rare in Europe: pyrocumulonimbus clouds, or "fire clouds," forming above the largest blazes.

These towering structures are self-feeding — they generate their own lightning, igniting new fires at a distance and transforming individual blazes into something closer to a weather system than a simple fire.