Severe wildfires that engulfed parts of western Canada this week were so intense that they generated massive "fire clouds" that spawned their own lightning storms.
In what some experts said was one of the most extreme events they've ever witnessed, more than 700,000 intracloud and cloud-to-ground flashes of lightning — from both fire clouds and regular thunderstorms — were recorded Wednesday over a 15-hour period.
"That's 5 percent of Canada's lightning in just 15 hours," said Chris Vagasky, a Colorado-based meteorologist with Vaisala, a Finnish company that specializes in weather and other environmental measurements.
Wildfires so extreme they create their own weather are not common occurrences, but with climate change making fires both more frequent and more intense, scientists say the risks of such events sparking out-of-control blazes will likely increase in the future.
A fire cloud, known as a pyrocumulonimbus cloud or pyroCb, typically forms when a fire rages with enough intensity that it creates updrafts of smoke, water vapor and ash that rise high into the atmosphere. These columns of air then cool and condense, forming clouds that can generate thunder, lightning and tornado-force winds.
Pyrocumulonimbus clouds are worrisome because they can cause wildfires to behave erratically, making it difficult for firefighters to control the blazes or predict how they will evolve. Fire clouds can also help wildfires spread by kicking up burning embers that land downwind or by producing lightning strikes that ignite new areas.
It's not well understood why some large fires create pyrocumulonimbus clouds and others don't, and it remains an active area of research. Scientists are also hoping to better understand the effect of climate change on the emergence of fire clouds.
In general, though, scientists have observed an increase in the frequency and intensity of wildfires as a result of global warming.
"As the Earth continues to warm, you tend to get drier periods that create more favorable conditions for wildfires," said Dakota Smith, a meteorologist based in Colorado. "If you're increasing the frequency of wildfires, you're also increasing the chance of extreme wildfire behavior."
The wildfires raging in British Columbia and Alberta developed on the heels of a historic heat wave that brought record-setting temperatures to the entire Pacific Northwest. It was that punishing heat that helped create ideal conditions for large fires to break out, said Mike Flannigan, director of the Canadian Partnership for Wildland Fire Science at the University of Alberta.
"It was a powder keg just waiting for a spark," he said.
Wildfires, regardless of where they occur, need three basic ingredients to thrive: vegetation — such as dried-out leaves, twigs, cones and dead trees — that act as fuel; conducive conditions like hot, dry and windy weather; and finally, some type of ignition such as lightning or a human-caused event.
The recent heat wave, which produced temperatures well over 100 degrees Fahrenheit for several days in parts of British Columbia, helped dry out the land and create a perfect storm of wildfire ingredients.
"The drier it is, the easier it is for a fire to start and spread," Flannigan said. "It also means there is more fuel available to burn and more energy being released, so you have a higher-intensity fire."
As such, when an ignition event occurs, the consequences can be devastating.
Nowhere was that more evident than in the village of Lytton, British Columbia, which set new national temperature records three days in a row, peaking at a scorching 121 degrees on Tuesday. A day later, a fast-moving wildfire tore through the area, forcing a mandatory evacuation order shortly before the entire town was consumed in flames.
Flannigan said it's unusual to see such severe wildfires in British Columbia this early in the summer. If conditions stay hot and dry, the region could be in for a punishing fire season.
"The risk is high and the potential for an extremely active season is there," he said. "In part, that's already being realized now."