SYDNEY—Wildfires ravaging much of southeastern Australia burned so hot that they created their own thunderstorms and lightning—similar to conditions during a volcanic eruption or atomic bomb blast.
Firefighter Michael Brearley was leading the defense of Wingello, a small town around 100 miles south of Sydney when a huge cloud began to form in the distance on Saturday. He knew it was bad news: The area had barely seen a drop of rain for weeks.
Instead it was fire that rained down from the formation of pyrocumulonimbus clouds—created by intense heat driving air rapidly upward in the smoke plume from a wildfire, drawing in moisture and resulting in thunderstorms. Scientists say they are only beginning to understand the weather phenomenon, making its behavior hard to predict.