The day after Klimek found the single tree on fire, he talked things over with Eric Hensel, the fire-management officer at Lassen Volcanic National Park. Among other things, they considered the point of ignition, the surrounding topography and forest, current drought conditions and the potential places where a team could create breaks in the trees to contain the fire. They consulted with the National Park Service’s regional fire ecologist and regional fire management officer, in San Francisco, then presented their findings to the park superintendent. The nearest town was more than 10 miles away, and a lot would have to go wrong before the fire could get close to it. The group decided to manage the fire rather than put it out right away.

Five days later, the fire was doing just what they hoped. Klimek described it to me as “a low-intensity backing fire” — that is, one moving downhill rather than up; an uphill fire tends to spread faster. It was “cleaning up” underbrush and wood on the ground as it moved. On July 30, the fire’s extent was only three acres, and a person could still walk safely in its midst. (When officials describe a fire’s size in terms of acreage, it doesn’t necessarily mean every spot in that space is actively burning.) When I walked the area 10 months later with Scott L. Stephens, a professor of fire science at the University of California, Berkeley, and an expert on prescribed and managed fires, he said, “This looks exactly like what I would’ve aimed for if I were setting a prescribed fire in here.”

Hensel gave thought to initiating a “burnout operation” between the park road and the fire’s location. That would entail starting a second fire that would burn toward the existing one, thus reducing the risk that it would spread beyond a chosen limit, in this case the park road. This line of control was selected because there was a stand of lodgepole pines on the north side of the road. Unlike Ponderosa, Douglas firs and other conifers in the mountain West, lodgepoles are highly susceptible to fire, and this stand, nearly a hundred years old, had never burned; it was like a land mine waiting to be set off. But more thunderstorms were in the forecast, and the cold air they brought with them was likely to create a downdraft with the potential to spread the fire rapidly in any direction (and additional lightning strikes could also start more fires). It was this risk of its becoming unpredictable, Hensel later explained to me, that made a burnout unwise.

As Hensel weighed the options, Calvin Farris, the Park Service fire ecologist in charge of Lassen Volcanic, was working with an analyst who studies fire behavior for the Forest Service. They were using a computer model that Mark Finney helped develop, called FSPro (Fire Spread Probability), which predicts a wildfire’s likely movement, based on variables like topography, weather, the types of trees in a forest and how dry they are. In a typical year it works well, but for whatever reason, as August and its heat approached, that wasn’t the case. It was consistently underestimating the likelihood that particular areas would burn. This wasn’t unusual; at one point during the 1988 fires that burned nearly 800,000 acres in and around Yellowstone National Park, the statistician whose work underlies many fire-spread models used his own model to project where the fire would be in two weeks. It spread twice as far in the next 24 hours.

On Aug. 6, 2012, the weather in Lassen Volcanic National Park changed: the wind turned around and picked up significantly, blowing the fire across the road and into the lodgepole pines. Once the fire spread into the lodgepoles, it became very hard to control, because of the surrounding terrain and the weather at the time. The next day, a federal interagency fire-management team was brought in to coordinate suppression efforts. On Aug. 8, the fire expanded beyond the park’s borders, and it became a threat to the town of Old Station.

The new people in charge held a public meeting to inform area residents about the fire’s status and possible evacuation procedures. Both Hat Creek Valley and Old Station had evacuated their homes because of wildfires twice in the previous 10 years, most recently in 2009, when lightning ignited fires that burned 9,300 acres.

Darlene Koontz, who is the park superintendent at Lassen Volcanic, was in charge of some federal lands in New Mexico a few years after a prescribed fire there spread out of control and burned part of Los Alamos in 2000; 400 families lost their homes, and the fire’s total cost was estimated to be $1 billion. So she was familiar with balancing the risks in a drought-stricken forest and aware of the public outcry that could follow mistakes. Yet efforts to notify the community near the Lassen Fire were minimal, and reports in the local news media seemed to add a measure of anger to the public’s anxiety.