How to interpret ISI
Higher ISI values indicate greater potential for rapid initial spread when a fire is present. Because wind is an important input, ISI can change quickly as weather changes.
Fire weather is context, not a local prediction
ISI is not a forecast fire perimeter, rate-of-spread calculation for a specific incident, or route/community safety assessment. Actual fire behaviour depends on fuels, terrain, weather and the fire itself.
How ISI fits into CFFDRS
Canada's Fire Weather Index System connects weather observations to fuel-moisture codes and fire-behaviour indices. FireRadar keeps each component separate so users can see what is actually being measured or derived instead of receiving an opaque combined risk score.
Use official operational guidance for decisions
CWFIS products are broad national fire-weather guidance. Provincial, territorial, Indigenous, municipal and Parks Canada authorities remain responsible for operational fire danger, restrictions, wildfire response and emergency decisions.
Official methodology and source
FireRadar renders the official Natural Resources Canada CWFIS layer directly and preserves the upstream symbology. It does not interpolate a value when the source is unavailable or transform this component into a FireRadar property-risk score.