Ministry of Forests, Lands and Natural Resource Operations - Wildfire Management Branch

Fire Weather Index System

The Canadian Forest Fire Danger Rating System (CFFDRS) system provides a uniform, numeric method of rating fire danger throughout an area; it is dependent on weather only and does not consider differences in risk, fuel, or topography. Its six components are:

FFMC - Fine Fuel Moisture Code
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.
DMC - Duff Moisture Code
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.
DC - Drought Code
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.
ISI - Initial Spread Index
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.
BUI - Build Up Index
A numerical rating of the total amount of fuel available for combustion that combines DMC and DC.
FWI - Fire Weather Index
A numerical rating of fire intensity that combines ISI and BUI. It is suitable as a general index of fire danger throughout forested and rural areas.