Fire Danger Rating (FDR)

Fire Danger Rating (FDR) is a measurement used by the Georgia Forestry Commission (GFC) to gauge the behavior of fire - before it starts. Fire danger ratings integrate the effects of fuels, topography and weather into numerical indices that provide an indication of how readily a fire will ignite and of fire behavior (spread intensity) after it starts. FDR is actually NFDRS for National Fire Danger Rating System, which is a system used nationally by all fire agencies.

Fire danger ratings are calculated on a day-to-day basis and are subject to change with weather conditions. FDR is classified numerically from 1 to 5 or by using defined color codes.

Classification Levels

Class day 1 - Low

Fires do not readily start and fires that do start spread slowly with low resistance to control. There is little danger of fire spotting. Prescribed burns can be executed with reasonable safety.

Class day 2 - Moderate

Fires can start from most accidental causes, but the number of starts is generally low. Fires burn at moderate intensities; heavy fuel concentrations will burn hot. Fires are not likely to become serious and control is relatively easy. Prescribed burns can be executed with reasonable safety.

Class day 3 - High

Fires start easily from most causes. Unattended brush fires and campfires are likely to escape. Fires spread rapidly and short-distance fire spotting is common. Fires may become serious and their control difficult unless they are attacked successfully while small. Prescribed fire objectives are frequently met on Class 3 days but care must be taken to keep fire within control boundaries.

Class day 4 - Very High

Fires start readily and spread quickly. Spot fires are a constant danger and fire behavior is often erratic. Resistance to control is high, as is the potential for large fires. Site specific conditions and land management objectives may warrant prescribed burning by experts, but care must be taken to keep fire within boundaries.

Class day 5 - Extreme

Fires start and spread quickly and burn intensely. All fires are potentially serious or disastrous. Direct attack of fires is virtually impossible and fires often escape initial attack. Fire behavior is erratic and "blow ups" may be expected. Fire restrictions may go into effect. Experienced professionals may conduct successful prescribed burns after considering site specific fire danger and taking extra precautions to control fire.

Little Known Facts about Fire Danger:

  • Georgia uses 19 weather stations to measure fire danger on 37 million acres. This means that fire danger is general over large areas, not specific to any particular site.

  • In rating Fire Danger, Forest Rangers give consideration to fire danger trends over several days as well as to specific daily factors that influence wildfire risk.

  • Wind is the strongest contributing factor to high fire danger. Fire danger is frequently considered high following a windy frontal passage, even if the front brought rain.

  • Forest fuels are classified according to how long it takes their moisture content to equalize with the surrounding air. Grass and straw are one hour fuels. Small twigs are 10 hour fuels. Dead limbs are 100 hour fuels. Logs are 1000 hour fuels. Daily fire danger may not be a good indication of fuel moisture.

  • Red Flag warnings normally coincide with high fire danger but do not reflect site specific conditions.