How Bad Is the Bootleg Fire? It’s Generating Its Own Weather.

A towering cloud of hot air, smoke and moisture that reached airliner heights and spawned lightning. Wind-driven fronts of flame that have stampeded across the landscape, often leapfrogging firebreaks. Even, possibly, a rare fire tornado.

The Bootleg Fire in Southern Oregon, spurred by months of drought and last month’s blistering heat wave, is the largest wildfire so far this year in the United States, having already burned more than 340,000 acres, or 530 square miles, of forest and grasslands.

And at a time when climate change is causing wildfires to be larger and more intense, it’s also one of the most extreme, so big and hot that it’s affecting winds and otherwise disrupting the atmosphere.

“The fire is so large and generating so much energy and extreme heat that it’s changing the weather,” said Marcus Kauffman, a spokesman for the state forestry department. “Normally the weather predicts what the fire will do. In this case, the fire is predicting what the weather will do.”

The Bootleg Fire has been burning for two weeks, and for most of that time it’s exhibited one or more forms of extreme fire behavior, leading to rapid changes in winds and other conditions that have caused flames to spread rapidly in the forest canopy, ignited whole stands of trees at once, and blown embers long distances, rapidly igniting spot fires elsewhere.

“It’s kind of an extreme, dangerous situation,” said Chuck Redman, a forecaster with the National Weather Service who has been at the fire command headquarters providing forecasts.