Fire danger is not the same as an active fire
The Fire Weather Index is a numeric rating derived from weather and fuel-moisture components. Natural Resources Canada describes FWI as an overall measure of potential fire intensity in a standard pine-forest context. Higher values indicate greater potential intensity and larger flames if a fire is burning; they do not prove that a fire has started at a location.
Temperature, relative humidity, wind speed, and rain feed the FWI System. The system also tracks fine-fuel moisture, deeper drying, expected spread, and available fuel through related codes and indices.
Official source-rendered guidance, kept separate
FireRadar requests the CWFIS FWI map directly from Natural Resources Canada’s public mapping service and preserves the source-rendered symbology. FireRadar does not convert the layer into a property-risk score, predict ignition, infer evacuation risk, or merge the index into current-fire totals.
This route intentionally does not print a “current as of” time unless FireRadar has independently validated one from the product. A successful map request shows the upstream layer; if the source is unavailable, FireRadar does not substitute a guessed value.
Why fire weather varies across Ontario
Ontario's fire environment ranges from the heavily populated south to the vast forests, peatlands, lakes, and remote communities of the north. Fire-weather conditions in Northwestern and Northeastern Ontario can be very different from conditions around the lower Great Lakes. Ontario Aviation, Forest Fire and Emergency Services remains authoritative for provincial fire danger and operational guidance.
Important limitations
FWI is broad fire-weather guidance, not a parcel-level threat forecast and not a measure of whether a particular wildfire will spread toward a community. Fuel type, terrain, local weather, suppression activity, fire behaviour, and many other factors matter. Follow the responsible provincial, territorial, Indigenous, municipal, and emergency authorities for restrictions and operational decisions.
Official methodology and source
The Fire Weather Index System is a main component of Canada’s Canadian Forest Fire Danger Rating System. Natural Resources Canada documents the moisture codes and fire-behaviour indices used to produce FWI and publishes daily national fire-weather information through CWFIS.