Media Guide to Forest Fires - Fire Weather Indicies

These codes and indices are indicators of the dryness of the forest fuels, and give relative measure of the burning conditions that can be expected for a "standard" fuel type. Low numbers mean wet conditions. High numbers mean dry conditions.

The individual fields are:
1. Fine Fuels Moisture Code (FFMC)     Range: 0-100
The dryness of the smallest forest fuels (surface litter, leaves, needles, small twigs, etc.). Derived from yesterday's FFMC, and the local noon temperature, relative humidity, wind speed and 24-hour precipitation.

2. Duff Moisture Code (DMC)     Range: 0-Unlimited
The dryness of the medium sized surface fuels and duff layers (the layer of partially and fully decomposed organic materials lying below the litter and immediately above the mineral soil). Approximately 2-10 cm in depth). Derived from yesterday's DMC, and the local noon temperature, relative humidity, and 24-hour precipitation.

3. Drought Code (DC)     Range: 0-Unlimited
The dryness of the largest sized surface fuels and deep duff layers. (Approximately 10+ cm in depth). Derived from yesterday's DC, and the local noon temperature, and 24-hour precipitation.

4. Initial Spread Index (ISI)     Range: 0-Unlimited
A relative measure of how quickly a wildf re can be expected to spread. Derived from the FFMC and wind speed.

5. Build Up Index (BUI)     Range: 0-Unlimited
A relative measure of the amount of fuel available for combustion. Derived from the DC and DMC.

6. Fire Weather Index (FWI)     Range: 0-Unlimited
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.

Numerical minimums for each danger class.

Nova Scotia Low Moderate High Extreme
FFMC 0.0 80.9 86.9 90.0
DMC 0.0 15.9 30.9 51.0
DC 0.0 140.0 240.0 341.0
ISI 0.0 2.2 5.0 10.0
BUI 0.0 20.0 36.0 61.0
FWI 0.0 3.0 10.0 23.0