Limiting global warming to 1.5 °C minimises projected global increases in fire weather days, but adaptation to new fire regimes is still needed

Understanding future shifts in fire weather risk, including peak season, transitional and off-season, will be crucial for reshaping fire preparation and management in order to adapt to climate change. This study explores future climate-driven projections of fire weather using the McArthur Forest Fire Danger Index (FFDI) across three Global Warming Levels (GWLs) with two future emissions scenarios – 1.5 °C, 2.0 °C under both RCP2.6 and RCP8.5, and 4.0 °C under RCP8.5. Using a large, perturbed physics ensemble, we assess uncertainty in fire weather projections globally and for three regions: Australia, Brazil, and the USA. In addition to season length and peak FFDI, we evaluate transitions in meteorological fire danger periods and shifts in low-fire weather windows to inform fire management throughout the annual cycle. We project a global rise in fire weather days and severity at all GWLs, with the largest increases in Australia, followed by Brazil and the USA. At 1.5 °C, the area exposed to Very High fire weather (FFDI ≥ 24) expands by 31 % (25 %–36 %) relative to a baseline of 1986–2005. Higher GWLs drive further increases, with more than a threefold rise in Very High fire weather days from 2.0 °C to 4.0 °C, emphasising the mitigation benefits of limiting global warming to well below 2.0 °C as intended by the Paris Agreement. The transition from High to Very High, a proxy for the start of the fire season, advances, by 9–12 days in Australia, 16–22 days in Brazil, and 8–24 days in the USA. Despite these changes, low-fire windows persist, providing crucial opportunities for out-of-season preparation such as controlled burns. Our findings highlight the need for both emissions reductions and adaptive strategies, including accounting for changes in out-of-season fire risks when employing management techniques that rely on pre-fire season preparations.