Abstract

Surface winds are an important factor in wildfire growth and the decision-making process of when utility companies shut off power to suppress fire ignitions. However, long-term trends in surface winds and their implications for fire weather have received less attention compared to trends in temperature, humidity, and precipitation. This article uses the ERA5 reanalysis to calculate surface wind trends over California during 1979--2019. We find statistically significant increases in surface easterlies during autumn on the western slopes of the Sierra Nevada Mountains and increases in Hazardous Wind Events of heightened wind-related fire risk. Using the Canadian Fire Weather Index, we also show that wildfire risk has mainly increased over the Sierra Nevada Mountains, indicating that strengthening winds has contributed to a growing risk of wind-driven wildfires in this region compared to 40 years ago.