Fig. 2: Standardized anomalies of hydro-meteorological and land-surface drivers on wildfire start days in comparison to non-wildfire days.

We show 2-m maximum temperature (Tmax), 2-m vapor pressure deficit (VPD), 10-m surface wind speed (WindS), 32-day accumulated (GPP-1M), 3-month SPEI (SPEI-3M), soil moisture (SoilM), and snow depth (SnowD) on the start day of wildfires in comparison to days without wildfires for each region and season over the entire subregion (“Over all” panel; left), mountain regions (“Mountains panel”; middle left) and non-mountain regions (“Non-mountains”; middle right). Colored values are based on the seasonal median difference between all wildfire start events and all non-wildfire events. The right panel (“On wildfire start days”) shows the difference between mountain regions and non-mountain regions on wildfire start days. Hatching indicates that the difference between wildfire start and non-wildfire days (first three panels from left) and mountain vs non-mountain regions (right panel) is not significant (Mann–Whitney U-test, p-value ≤ 0.05). Gray panels indicate that no events are observed in this region and season. To have a uniform sign across all variables, we flip the sign for deficit variables and mark these with an asterisk (*), i.e., SPEI-3M soil moisture and snow depth.