Containing wildfires—never mind extinguishing them—in parched and windy conditions can be monstrously difficult. Dry vegetation is rocket fuel for blazes and wind both feeds the flames and spreads the embers. “The winds are like pointing an air blower at a fireplace,” says Gershunov, “except it’s not contained and it’s on a much larger scale.”

Firefighters on Wednesday confronted persistently strong and dry winds fueling two giant wildfires that have terrified Los Angeles for eight days, testing the resolve of a city upended by the worst disaster in its history.