When catastrophic wildfires capture global headlines, such as the unprecedented blazes sweeping through southern Europe this summer or the devastating 2019–20 “Black Summer” in Australia, they are almost always preceded by severe drought. Dry vegetation and parched landscapes are necessary ingredients for infernos.

But not all droughts are created equal – the way a drought evolves can drastically alter how a fire behaves once it ignites. As global temperatures rise, a new and dangerous phenomenon is becoming increasingly common: the “flash drought”.

Unlike standard droughts, which take place over months or years, flash droughts are rapidly occurring dry spells, driven by intense heat and unusually low humidity. They suck moisture out of the landscape at an alarming rate.

While scientists know standard droughts increase fire risks, a critical question has remained unanswered: do flash droughts further increase this risk, and what happens when these two drought types collide?

Our latest research mapped two decades of global satellite data to answer this question. We found when landscapes transition from a prolonged standard drought into a rapid flash drought – or when the two overlap – they create a “hyper-flammable” state.........

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