Fire Weather: On the Front Lines of a Burning World

by John Vaillant

that is what is different about the twenty-first century. The highs are certainly higher, but it is the lows—in all seasons—that are, in their way, more disturbing. A typical spring night in Fort McMurray used to be in the 40s; in May 2016, nighttime temperatures barely dropped below 70°F. In Canada and northern Europe, nights during which the temperature stays above 68°F are referred to as “tropical.” Twenty years ago, Toronto might experience one or two tropical nights in the month of July; in 2020, it counted fourteen. During the same month, Phoenix, Arizona, sustained an average twenty-four-hour temperature of 99°F for the entire month, a new record. Not only can fire sustain itself much more easily in warm temperatures, but ice, snow, rain, and dew will all melt and evaporate more quickly (as will lakes and rivers), making all fuels easier to ignite.