<i>This fire, as fire scientist Craig Clements would later conclude, had grown too hot. Instead of slowing the fire, the oncoming dew boiled off the flame front like water off the rocks of a sauna, sending a pulse of superheated steam almost to the borders of space. As it pillowed up against the frigid edge of the earth’s atmosphere, the steam condensed and fell as hail, pushing a mass of frigid air down on top of the wildfire.</i><p><i>In any combustion reaction, more compression means more heat and power: The downrushing front made the difference between wildfire and blast furnace. On the video feed from Pedrógão Grande, Castellnou watched the collapsing downburst depress the fire column horizontally toward the trees, now clogged with cars. At around nightfall they caught, and within minutes 8 square kilometers of woodland, packed with fleeing vacationers, burst into flame.</i><p>Terrifying.