Fire Weather Forecast Maps and Indices
The following is a list of Fire Weather Maps and Indices that are active during the forest fire season.
Weather conditions are constantly changing. This information has been prepared for your convenience and has no official sanction. For further information contact the Fire Control Centre.
Standard Components of the Fire Weather Index (FWI):
The six standard components of the FWI System provide numerical ratings of relative wildland fire potential. The first three components are fuel moisture codes that follow daily changes in the moisture contents of three classes of forest fuel with different drying rates. For each, there are two phases — one for wetting by rain and one for drying — arranged so that the higher values represent lower moisture contents and hence greater flammability. The final three components are fire behavior indexes, representing rate of spread, amount of available fuel, and fire intensity; their values increase as fire weather severity worsens.
The system is dependent on weather only and does not consider differences in risk, fuel, or topography. It provides a uniform method of rating fire danger across Canada. The six components are described below.
- Fine Fuel Moisture Code (FFMC)
A numerical rating of the moisture content of litter and other cured fine fuels. This code is an indicator of the relative ease of ignition and flammability of fine fuel.
- Duff Moisture Code (DMC)
A numerical rating of the average moisture content of loosely compacted organic layers of moderate depth. This code gives an indication of fuel consumption in moderate duff layers and medium-size woody material.
- Drought Code (DC)
A numerical rating of the average moisture content of deep, compact, organic layers. This code is a useful indicator of seasonal drought effects on forest fuels, and amount of smouldering in deep duff layers and large logs.
- Initial Spread Index (ISI)
A numerical rating of the expected rate of fire spread. It combines the effects of wind and FFMC on rate of spread without the influence of variable quantities of fuel.
- Buildup Index (BUI)
A numerical rating of the total amount of fuel available for combustion that combines DMC and DC.
- Fire Weather Index (FWI)
A numerical rating of fire intensity that combines ISI and BUI. It is suitable as a general index of fire danger throughout the forested areas of Canada.