Increasing Synchronous Fire Danger in Forests of the Western United States

Widespread fire activity taxes suppression resources and can compound wildfire hazards. We examine the geographic synchronicity of danger across western United States forests as a proxy for strain on resource availability. Interannual variability in number days with synchronous danger, defined weather indices exceeding local 90th percentile ?40% forested land, was strongly correlated (r = 0.85) high national management resources. A 25-day increase annual observed during 1979–2020. Climate projections show doubling such by 2051–2080. Such changes will escalate likelihood years extended periods that have historically strained efforts contributed to additional burned area, therein requiring strategies coping anticipated surges demands.