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

中文翻译：

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美国西部森林中的同步火灾危险增加

广泛的消防活动给抑制资源带来了税收，并可能加剧野火危害。我们研究了美国西部森林火灾危险的地理同步性，以作为抑制灭火资源有效性的替代方法。年际变化与同步火险天数，定义为火险气象指数超出跨越林地≥40％的当地90百分位，强烈相关（[R = 0.85），这对国家消防管理资源造成了很大压力。在1979-2020年期间，每年发生同步火灾危险的天数增加了25天。气候预测显示，到2051年至2080年，此类日子将增加一倍。这种变化将使同步火灾危险持续数年的可能性升级，这在历史上抑制了灭火工作，并增加了燃烧面积，因此需要额外的管理策略来应对预期的灭火需求激增。