Changes of extreme fire weather conditions in the contiguous United States

Fire weather conditions, including heat, humidity, rainfall, and wind speed, play a critical role in wildfire occurrence and burned area. By identifying extreme fire weather events based on their intensities and durations, we demonstrate that both the mean state and variability of daily fire weather conditions in the western United States have been shifting towards a more extreme and fire-prone regime since the 1980s. This shift is characterized by more frequent and intense extreme fire weather events in the region. These exacerbated fire weather conditions strongly correlate with expanding burned areas, increasing fire risk and potential damage.

However, fire risk does not increase monotonically with climate change. Our findings reveal that extreme fire weather conditions showed a decreasing trend before 1980, indicating that climate change alone cannot explain all the changes in extreme fire weather events. In our ongoing research, we will investigate how the phase changes of the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation relate to this decreasing trend.