Historic Wildfires 

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Understand the influence of historic wildfires on property level Fire Factor risk assessments.

Historic wildfires are incorporated in the First Street Foundation Wildfire Model to help inform wildfire fuels and potential ignition locations. Fuels in the Wildfire Model are based on the U.S. Forest Service’s LANDFIRE fuels dataset, however homes and other buildings are considered nonburnable fuels within LANDFIRE. To accurately model wildfires risk within the wildland-urban interface (WUI) 2,500 historic wildfires were analyzed to estimate the fuel type of properties within the WUI.

Fire Factor also provides information from previously recorded wildfires since 1984 and highlights the number of fires that have come within 20 miles of the property. 

How they were chosen

Fire Factor uniquely estimates wildfire risk to properties, homes and businesses within the Wildlands Urban Interface (WUI). The WUI is an area of transition, where houses and wildland vegetation meet or intermingle and where wildfires are most pronounced. 

Historical fires between 1992 and 2018 that were greater than 100 acres were selected to differentiate areas where suppression is less likely to occur, from areas where human-caused fires are more likely to occur.

Historic analysis 

Property-level Fire Factors are heavily dependent upon estimates of the type, quantity, age, and condition of burnable material and vegetation. Anything that can burn is fuel for a fire, including homes. Historic fires are used to estimate fuels and potential ignition locations within the WUI.

The Wildfire Model incorporates wildfire fuels, such as trees and other vegetation, based on the U.S. Forest Service’s fuels dataset. It also incorporates homes as potential fuels for wildfire spread to other homes from looking at patterns in 2,500 historic wildfires. The location and intensity of historic fires are used to determine potential ignition locations, or areas that are likely to burn based on the nearby vegetation and fuel sources.

Historic fires on Fire Factor

Using probable ignition locations based on historic fires, the model then considers past weather patterns that impact fuels by making them hotter and drier, as well as the type of weather that helps spread fires further such as wind. The building’s location is then used to determine the likelihood of the home being in a wildfire based on how many times the 8 million simulated fires reached it. This allows Fire Factor to determine risk based on a home’s probability of being in a wildfire, the fire intensity, and the exposure to flying embers. 

Property and building damage from historic fires are also used to guide which building characteristics have the biggest influence on building survival in a wildfire. Analysis of data describing buildings lost or damaged at historical fires provided guidance on the most significant characteristics related to building survival in a wildfire. 

The First Street Foundation National Wildfire Model is a first of its kind, nationwide, behavioral wildfire model that shows a specific location’s probabilistic risk of wildfire based on the vegetation, topography, and fire weather in the surrounding area. It builds off of decades of peer-reviewed research and forecasts how wildfire risks will change over time due to changes in the environment. Use Risk Factor to find property-specific wildfire risk assessments for any U.S. address.


Learn more

How is my Fire Factor Calculated?

The methodology behind Fire Factor

Where does the information on Fire Factor come from?



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