Embedded Files
The National Fire Danger Rating System (NFDRS) uses weather, fuels, and fire occurrence data to calculate fire danger for a given area. Widely used across the United States, the NFDRS was recently updated to improve estimates of fuel moisture and simplify fuel model inputs.
In the United States, the National Fire Danger Rating System (NFDRS) has been used to support operational fire decision making for the last 50 years. The NFDRS was first created in 1972, with updates in 1978 and 1988. The latest version (NFDRS2016) was released for operational, nationwide use in 2023. Daily outputs from the NFDRS are used to maintain wildland fire situational awareness, respond to wildfire incidents, plan for and safely conduct prescribed fires, and inform the public about wildfire potential (low to extreme) through signage commonly seen on National Forests.
The four main factors for rating determinations are:
Size and shape of fuels
Compactness or arrangement of fuels
Fuel moisture content
Fuel temperature.
In general, these factors vary over a geographic area, change each day, and are not practical to continually assess. Therefore, fire danger rating signs will display the Fire Danger Rating using air temperature. Wind is the most influential factor affecting wildfire spread.
Any reliable weather forecast can be utilized and when in doubt, round up to the next higher rating. Windy periods with low fuel moisture and relative humidity usually result in Red Flag Warnings. Red flags will only be displayed when the National Weather Service declares a “Red Flag Warning” for any portion of Polk County. The rating will be “Extreme” when red flags are posted regardless of other weather conditions.
Signs will change to “low” when there is sustained rain (over 4 hours).
Sign is kept at low unless weather associated with increased wildfire ignition and fuel conditions support changing. This will be a discretionary decision by the fire agencies and will be considered during significant dry periods during the winter months where prescribed burning increases wildfire ignition potential.
Fire Danger Rating and Color Code Description
Four color-coded fire danger levels are used to help the public understand fire potential and current conditions. This information is essential for preventing human-caused wildfires.
Low (L) (Green): At the "Low" level, fuels do not ignite easily from small embers, but more intense heat sources, such as lightning, may start fires in duff or dry rotten wood. Fires in open, dry grasslands may ignite a few hours after rain, but most wood fires will spread slowly, either creeping or smoldering. Fire control is generally easy.
Moderate (M) (Blue): With a "Moderate" fire danger, fires can start from most accidental causes, though the number of fire starts is typically low. If a fire ignites in an open, dry grassland, it will burn and spread quickly on windy days. Most wood fires will spread slowly to moderately, with average intensity remaining moderate, except in heavy fuel concentrations, which may burn hotter. Fires are generally manageable.
High (H) (Yellow): At the "High" level, fires can easily ignite from various causes, with small fuels like grasses and needles catching fire readily. Unattended campfires and brush fires are likely to escape. Fires will spread easily, with some areas exhibiting high-intensity burning on slopes or concentrated fuels. These fires can become serious and difficult to control if not extinguished promptly.
Extreme (E) (Red): At the "Extreme" level, fires of all types ignite quickly and burn intensely. All fires are potentially serious and can spread rapidly. Small fires can escalate into larger ones much faster than at the "Very High" level. Spot fires are likely, with long-distance spotting expected. These fires are very difficult to combat and may pose significant danger, lasting several days or weeks.
During fire season, even small sparks can lead to dangerous wildfires, making fire prevention critical. Whether it's maintaining safe campfires, using outdoor equipment responsibly, or properly discarding smoking materials, taking precautions can help reduce the risk of human-caused fires. Staying informed about current fire danger levels and following local regulations is key to keeping the community safe.
Other Resources:
Page updated
Google Sites
Report abuse