What is “fire weather” and why is it getting worse?

The map above visualizes when these three variables — temperature, humidity, and wind — combine to produce days with fire, shown as a percentage change since 1973. All parts of Colorado have experienced at least 100 percent more days on fire. Texas also looks bleak, with the southern end of the state seeing an increase of 284%. Central California is on a similar issue, with a 269 percent jump on fire days. “The Southwest really came out first,” Weber said. “We even see some parts of Oklahoma and Kansas, some of those places where we don’t traditionally think about fires.”

But if you’re wondering why we don’t often hear about catastrophic fires in the plains, as we do in California, Oregon and Colorado, it’s because “fire weather” just means the conditions are right for a fire – it doesn’t mean they necessarily happen. “We are not talking about ignition on fires, ”says Weber. “We are talking about the number of days in the year during which the meteorological elements prepare the landscape for these high-risk fires, which are really more dangerous to fight and really harder to fight.

Atmospheric conditions are not the only variables that exacerbate the likelihood of fires. Land management decisions in California and Oregon, for example, play a role. These coastal areas are covered with forests that were once regularly burned in a healthy way: Lightning would cause a relatively small fire that chewed through a brush, clearing the way for new growth but leaving very mature trees alive. Historically, Native Americans have also set fire to targeted fires to strategically rebuild ecosystems. The landscape burned a lot, but this also meant that it burned less intensely, as the flammable brush had no chance of accumulating between burns.

But over the past century, farmers have taken the opposite approach: putting out a fire or putting out immediately anything that could affect residential areas. This allows the accumulation of dry vegetation – more fuel. And with more human communities living in the “urban interface of wildlife,” where the forest meets cities, people are also more likely to start random fires, whether they’re from a cigarette zipper thrown out a window or a faulty electrical infrastructure.

That’s part of the reason fires are so much more catastrophic in California than in Kansas or Oklahoma: There are just a lot more forests with a lot more fuel and more people living in danger. To adapt, land managers in the western states need to carry out more controlled burns, which will clean the brushes, as often, smaller forest fires.

Climate change has also forced some seemingly contradictory seasonal changes. As the warmer atmosphere retains more water, quantity The rainfall may actually increase in the future until length the wet season shrinks. In California, rains usually arrive in October and last until March. Now they come later in the year. “The dry season will extend to the usual wet season,” said climatologist Ruby Lung of the Pacific Northwest National Laboratory. “When we look at the climate models that are projected in the future, the fire season will be extended.”

Firefighters are already seeing this happen. California used its biggest flames in the fall, just before the seasonal rains came, when the landscape was further dry for half a year without water. This coincided with fierce seasonal winds that would cause huge forest fires. But now, because the rainy season is so short and the landscape has more than a year to dry, the fire season comes even earlier. “What we see more consistently and more regularly is the fact that these fires are getting bigger and bigger, sooner than they normally would in the past,” said Isaac Sanchez, the battalion’s communications chief. at the California Department of Forestry and Fire Protection, told WIRED earlier this month. “So when August is rolling, at the end of July it’s rolling, we see these dry conditions that are absolutely the result of climate change.”