While the Severity group focuses on the behavior of a wildfire, if one occurs, Frequency group elements reflect the likelihood of wildfire occurrence. Both severity and frequency contribute to the overall risk that a structure faces due to wildfire. In fact, the components of the Severity and Frequency groups represent a significant portion of the weighting in the overall rating.
Frequency factors are diverse and include historic burn areas, proximity to transmission lines (as a potential ignition source), ignition probability (based on temperature and moisture), and probabilistic modeling indicative of potential return interval. The assumption is that if a collection of circumstances which generated wildfires elsewhere exists, the same thing could happen with an increased likelihood in the future.