Winter wildfire in the United States

Image Source: San Francisco Chronicle

Wildfire is becoming more frequent and widespread across the United States due to climate change. Fire seasons are also growing longer, with destructive fires occurring earlier and later in the year. Colorado's Marshall Fire, which burnt more homes than any other fire in state history and caused two deaths, ignited on December 30th, well outside of the historical Colorado Fire Season.

Fires in January are increasing

January wildfires are most common in the Southeast, where relatively warm temperatures and a lack of snowfall allow for fire. But as winters grow warmer, the pattern of winter wildfires is changing.

Figure 1. Change in mean annual January fires. January fires are becoming less frequent in the Southeastern United States and more common in watersheds that span the Plains states and eastern Rocky Mountains, the desert Southwest and California.

Data Sources:

• Watershed Boundaries: United States Geological Survey Water Boundary Dataset
• Wildfire Occurrence: Short, Karen C. 2022. Spatial wildfire occurrence data for the United States, 1992-2020 FPA_FOD_20221014. 6th Edition. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2013-0009.6

No snow, more fire?

The Western United States is seeing increasingly frequent winters with little or no snow on the ground, and these conditions are expected to become more persistent with further warming of the atmosphere. Snow-free winters will continue to have an impact on wildfire timing, frequency and severity, potentially intensifying wildfire activity throughout the year--including during the winter.