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BackgroundLarge-scale meteorological patterns (LSMP) have been linked to variation in fire weather, wildfire ignitions, and burned area. However, the influence of multi-day sequences of these patterns on wildfire spread events remains unclear. AimsThis study classifies multi-day LSMP sequences and assesses their influence on the likelihood of wildfire spread events in the Northwestern United States. MethodsWe employ a two-stage approach using self-organizing maps to classify multi-day LSMP sequences from 500 hPa geopotential heights. We then estimated the impact of these sequences on wildfire spread likelihood using regression analysis on 2003–2020 regional fire data. Key resultsCertain LSMP sequences, including persistent ridging, characterized by positive height anomalies over the region, are preferentially associated with wildfire spread events. ConclusionsClassifying multi-day LSMP sequences using self-organizing maps can potentially aid in forecasting wildfire spread events. ImplicationsFire weather meteorologists can apply this approach to identify and forecast conditions associated with potential wildfire spread events, enabling better coordination. 

Abstract We define fire weather waves as persistent extreme fire weather, which can intensify fire activity by sustaining exceptionally warm, dry, and windy conditions. Here, we use daily fire weather index, fire activity, and meteorological data to examine the impacts of fire weather waves on fires, as well as their patterns and trends across global terrestrial ecoregions. Fire weather waves account for only 4% of days but coincide with 26% of the area burned and nearly half of the top 1% most energetic fires in forested ecoregions. Compared with grassland and shrubland fires, forest fires exhibit a larger and more persistent increase in daily burned area in response to fire weather waves, particularly in Mediterranean forests. Fire weather wave frequency has significantly increased across most burnable lands during 1979–2024. Climate projections indicate that fire weather waves will increase throughout the 21st century. These findings underscore fire weather waves as an essential component of early warning systems to strengthen preparedness for extreme fires. 

While overall impacts of heatwaves have been extensively studied, the connection between heatwaves and wildfire activity remains relatively underexplored. We analyze links between heatwaves and both wildfire occurrence and growth across the western United States (WUS) and find that 42% of burned area during 2001–2024 occurred during and immediately following heatwaves. Heatwaves facilitate significant increases in daily burned area through meteorological and fuel flammability conditions that promote new ignitions and exacerbate ongoing fire activity, with effects persisting post-heatwave in most regions. In addition, heatwaves co-occur with increased cloud-to-ground lightning that can potentially increase ignitions. Last, we observe a 2.5-fold increase in burned area in WUS forests since 2001, with ~64% of this increase coinciding with heatwaves, but without corresponding increases in nonforests. The growing influence of heatwaves in shaping burned area in WUS forests has important implications for fire management and public health and can improve predictions of wildfire risk. 

Abstract Tropical cyclones (TCs) are major drivers of contiguous United States (CONUS) flooding, yet their contribution to hourly precipitation extremes remains poorly quantified. Here we link observations from 420 gauges (1980–2024) with TC track data to attribute extreme hourly precipitation to both local and remote TCs. Remote TC contributions are identified via atmospheric river (AR) objects using the TempestExtremes framework applied to a global AR database. We identify 254 TCs that contributed to extreme hourly precipitation, affecting 76% of stations. While local contributions from Atlantic TCs are prevalent in eastern CONUS, remote influences from Pacific TCs contribute to precipitation extremes in the rest of CONUS. The number of TCs resulting in extreme hourly precipitation has increased significantly in northeast and southeast CONUS since 1980. These results reveal that TC‐linked moisture represents a contributor to short‐duration precipitation extremes across a broader area of CONUS than previously recognized. 

Concurrent extreme fire weather creates favorable conditions for widespread large fires, which can complicate the coordination of fire suppression resources and degrade regional air quality. Here, we examine the patterns and trends of intra- and interregional synchronous fire weather (SFW) and explore their links to climate variability and air quality impacts. We find climatologically elevated intraregional SFW in boreal regions, as well as interregional synchronicity among northern temperate and boreal regions. Significant increases in SFW occurred during 1979 to 2024, with more than a twofold increase observed in most regions. We estimate that over half of the observed increase is attributable to anthropogenic climate change. Internal modes of climate variability strongly influence SFW in several regions, including Equatorial Asia, which experiences 43 additional intraregional SFW days during El Niño years. Furthermore, SFW is strongly correlated with regional fire-sourced PM_2.5in multiple regions globally. These findings highlight the growing challenges posed by SFW for firefighting coordination and human health. 

Abstract Regions across the globe have experienced devastating fire years in the past decade with far-reaching impacts. Here, we examine the role of antecedent and concurrent climate variability in enabling extreme regional fire years across global forests. These extreme years commonly coincided with extreme (1-in-15-year) fire weather indices (FWI) and featured a four and five-fold increase in the number of large fires and fire carbon emissions, respectively, compared with non-extreme years. Years with such extreme FWI metrics are 88-152% more likely across global forested lands under a contemporary (2011–2040) climate compared to a quasi-preindustrial (1851–1900) climate, with the most pronounced increased risk in temperate and Amazonian forests. Our results show that human-caused climate change is raising the odds of extreme climate-driven fire years across forested regions of the globe, necessitating proactive measures to mitigate risks and adapt to extreme fire years. 

Abstract Previous research has examined individual factors contributing to wildfire risk, but the compounding effects of these factors remain underexplored. Here, we introduce the “Integrated Human-centric Wildfire Risk Index (IHWRI)” to quantify the compounding effects of fire-weather intensification and anthropogenic factors—including ignitions and human settlement into wildland—on wildfire risk. While climatic trends increased the frequency of high-risk fire-weather by 2.5-fold, the combination of this trend with wildland-urban interface expansion led to a 4.1-fold increase in the frequency of conditions conducive to extreme-impact wildfires from 1990 to 2022 across California. More than three-quarters of extreme-impact wildfires—defined as the top 20 largest, most destructive, or deadliest events on record—originated within 1 km from the wildland-urban interface. The deadliest and most destructive wildfires—90% of which were human-caused—primarily occurred in the fall, while the largest wildfires—56% of which were human-caused—mostly took place in the summer. By integrating human activity and climate change impacts, we provide a holistic understanding of human-centric wildfire risk, crucial for policy development.