A severe wildfire near Saumos in southwestern France became intense enough to generate a pyrocumulonimbus cloudA fire cloud, or 'pyrocumulonimbus', is a thunderstorm made by a big wildfire. Before the fire built a storm, Europe had become a tinderboxTowering smoke clouds rise above a wildfire as beachgoers look on in Southern France. It can generate powerful winds, lightning and even spark fresh fires.Nasa has called it the "fire-breathing dragon of clouds", and the name fits. In southwestern France, the Gironde fires have burned through 42,000 hectares, an area around four times the size of Paris. Similar questions are now being asked in Europe after France recorded its first such event.For firefighters, the concern is immediate.