This wasn't supposed to be a bad year for Western wildfires.
Last winter, a weak La Niña bloomed across the Pacific. It sent flume after flume of rain to North America and irrigated half the continent. Water penetrated deep into the soil of Western forests, and mammoth snow drifts stacked up across the Sierra Nevadas. California's drought ended in the washout.
Yet fires are now raging across the West. More than two dozen named fires currently burning across Washington and Oregon. More than one million acres have burned in Montana, an area larger than Rhode Island, in the Treasure State's third-worst fire season on record. And the largest brush fire in the history of Los Angeles currently threatens hundreds of homes in Burbank.
Canada may be experiencing an even worse year for wildfires: 2.86 million acres have burned in British Columbia, the largest area ever recorded in the province.
So what happened? How did a wet Western winter lead to a sky-choking summer?
The answer lies in the summer's record-breaking heat, say wildfire experts. Days of near-100-degree-Fahrenheit temperatures cooked the Mountain West in early July, and a scorching heat wave lingered over the Pacific Northwest in early August.
"This will become an important year for [anecdotes about] the importance of temperature. Despite the fact that these forests were really soaked down this winter and spring, these heat waves have dried things out enough to promote really large fires," says Park Williams, a research scientist at the Lamont-Doherty Earth Observatory at Columbia University.