Central Oregon Interagency Dispatch Center

Current Conditions - Library

Fire Danger Ratings

A Fire Danger Rating level takes into account current and antecedent weather, fuel types, and both live and dead fuel moisture (Deeming and others 1977, Bradshaw and others 1984 ).

The adjective class rating (see table below) is a method of normalizing rating classes across different fuel models, indexes, and station locations. It is based on the primary fuel model cataloged for the station, the fire danger index selected to reflect staffing levels, and climatological class breakpoints. This information is provided by local station managers. About 90% use the Burning Index (BI); others use Energy Release Component (ERC). Staffing class breakpoints are set by local managers from historical fire weather climatology.

Rating Level Rating Defintion

Low

[ Graphic Icon ] Fire Danger Rating Symbol

Low - The color code is green.

Fuels do not ignite readily from small firebrands, although a more intense heat source, such as lightning, may start many fires in duff or punky wood. Fires in open cured grassland may burn freely a few hours after rain, but woods fires spread slowly by creeping or smoldering, and burn in irregular fingers. There is little danger of spotting.

Moderate

[ Graphic Icon ] Fire Danger Rating Symbol

Moderate - The color code is blue.

Fires can start from most accidental causes, but with the exception of lightning fires in some areas, the number of starts is generally low. Fires in open-cured grassland will burn briskly and spread rapidly on windy days. Woods fires spread slowly to moderately fast. The average fire is of moderate intensity, although heavy concentrations of fuel, especially draped fuel, may burn hot. Short-distance spotting may occur, but is not persistent. Fires are not likely to become serious, and control is relatively easy.

High

[ Graphic Icon ] Fire Danger Rating Symbol

High - The color code is yellow.

All fine dead fuels ignite readily and fires start easily from just causes. Unattended brush and campfires are likely to escape. Fires spread rapidly and short-distance spotting is common. High-intensity burning may develop on slopes, or in concentrations of fine fuel. Fire may become serious and their control difficult, unless they are hit hard and fast while small.

Extreme

[ Graphic Icon ] Fire Danger Rating Symbol

Extreme - The color code is red.

Fires under extreme conditions start quickly, spread furiously, and burn intensely. All fires are potentially serious. Development into high-intensity burning will usually be faster and occur from smaller fires than in the very high danger class. Direct attack is rarely possible, and may be dangerous, except immediately after ignition. Fires that develop headway in heavy slash or in conifer stands may be unmanageable while the extreme burning condition lasts. Under these conditions, the only effective and safe control action is on the flanks until the weather changes or the fuel supply lessens.