The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a)

Abstract. Wildfire regimes of the western United States (US) have changed dramatically since the 1980s but our understanding of the causes and effects of these changes is limited by a lack of a quality-controlled, publicly available database of wildfire events that (1) spans from the 1980s to present, (2) represents wildfires across a wide range of sizes, and (3) includes mapped fire perimeters and the area burned within. Here we present an updated and improved Western US MTBS-Interagency database (WUMI2024a) of wildfire occurrences, perimeters, and burned-area maps, covering the period 1984–2024 and the geographic domain of the 11 westernmost states in the contiguous US. The database represents 22,464 wildfires ≥1 km² in size, which we 10,300 wildfires), the maps of fire perimeters and area burned are based on 30-m satellite data provided by the US government’s Monitoring Trends in Burn Severity (MTBS) project, allowing our mapping and assessments of total area burned to account for unburned areas within fire boundaries. For another 24 % of fires, our database includes perimeter observations provided by non-MTBS sources, meaning that only 30 % of fire occurrences are without perimeter observations. For these fires we tentatively assume perimeters are circular centred on the ignition location. Fires without perimeter observations are compile by merging seven publicly available government databases. For over 46 % of wildfires in our database (more than relatively small and over 95 % of area burned in the database is associated with fires with observed perimeters. The fire perimeters and burned area maps will aid assessment of the landcover types that burn and can be used to improve simulations of how historical fires have affected ecosystems and smoke emissions. The WUMI2024a can be quickly updated as new and improved data become available. The WUMI2024a dataset and the code used to produce the dataset are available at http://datadryad.org/share/Ox4oxdwdrhkmjUTpke7QgkfF--h-RLRbmMzGBhSmOr4 (Williams et al., 2025).