ClimateCheck uses wildfire as one of our five indicators of climate risk. We base this measurement on the average percentage of the area around your property that will burn annually. Our analysis uses models that track changing temperatures, precipitation, atmospheric CO2 concentrations, and vegetation type and density.

In 2022, we are updating how we measure wildfire risk to better refine the spatial resolution of our models to better estimate individual property risk. Our new wildfire risk rating will improve on the precision of our previous model, which was limited to a resolution of 4.17 km2 (1.61 mi2). The new rating is composed of several different types of data in order to best model different elements of fire risk.

How our 2022 Update Measures Wildfire Risk

We use climate change projections of temperature, precipitation, relative humidity, and wind speed to estimate the Fire Weather Index (FWI). The FWI is a widely-accepted wildfire danger rating system metric which estimates the intensity of dangerous wildfire conditions. It is a daily numerical measure of fire danger with 4km spatial resolution that accounts for the effects of fuel moisture and wind on fire behavior and spread.

The ClimateCheck wildfire risk rating is based on estimating changes in daily FWI values. For each target year, we track the magnitude and frequency of “extreme” FWI days. We define extreme as the 99th percentile of FWI values. To estimate change in frequency, we calculate the number of days per year which exceed the historical extreme magnitude.

FWI estimates are at too coarse a spatial resolution for property-level risk assessment. We have therefore integrated our model with the recently released 30m resolution 2020 US Forest Service (USFS) wildfire risk data products. These products include risk measurements such as:

  • Burn Probability: the chance of a wildfire starting (frequency)
  • Flame Length Exceedance Probability: likelihood that flame length exceeds a certain height (intensity)
  • Conditional Risk to Potential Structures: the damage if a house were present and a fire occurred (severity)

The Future of our Wildfire Risk Measurement

Fires are becoming more widespread and difficult to extinguish, due in part to the influence of climate change. It is important to estimate how the dangers of wildfire events will shape our individual homes and property in the future.

Our wildfire measurement model takes the change in wildfire danger in the future, as estimated by FWI, and integrates it with USFS products representing wildfire likelihood, intensity, and severity. The integrated product is at a high enough spatial resolution for us to assess risk based on the environmental context for a specific property. We are excited to deliver this best-in-class data and continue to improve our wildfire risk rating.

In summary, the new wildfire risk rating will excel at estimating:

  1. Property-level differentiation in wildfire risk
  2. Frequency and intensity of extreme wildfire danger conditions over the 21st century
  3. Current wildfire risk characteristics