The National Fire Danger Rating System (NFDRS) is used to estimate the risk of fire in a given area. It helps fire managers to determine the risk and allows them to prepare accordingly, whether that means closing public lands during high-risk periods or ensuring that staff are trained and the necessary equipment is prepared.
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What is the National Fire Danger Rating System (NFDRS)?
The NFDRS has 5 levels, each referencing a specific type of fire risk based on weather and fuel conditions. It was first implemented in the early 1970s and was later revised and reissued. By paying attention to the NFDRS, homeowners and campers can avoid starting fires during high-risk periods, thus reducing the risk of wildfire.
There are five levels, each represented by a colored flag and each denoting a specific risk.
Fire Danger Rating 1: Low (Green)
The lowest fire danger level. Fires are unlikely and controlled burning is okay providing it is executed safely and with care.
What is a Level 1 Fire?
At fire danger level 1, fires only start with an intense heat source, such as lightning. There is also a greater risk of fires in dry wood that has been destroyed by insects. Fires spread slowly at this level.
Fire Danger Rating 2: Moderate (Blue)
Fire danger level 2, represented by a blue flag, indicates an increased level of risk, although the chance of fire is still low.
What is a Level 2 Fire?
Lightning fires can occur. There is also a risk of fire from many accidental causes, but this risk is fairly low.
There will be a moderate flame length and a moderate rate of spread, but most fires will be easy to control and shouldn’t cause too many problems.
Fire Danger Rating 3: High (Yellow)
The chance of fire is much higher than at previous fire danger levels and these fires could spread. Caution is advised. Outdoor burning should be limited to the early morning and late evening.
What is a Level 3 Fire?
A fire that starts in a level 3 area may spread rapidly and be difficult to control if it is not caught early. Spotting may occur over a short distance.
Fire Danger Rating 4: Very High (Orange)
Level 4 on the National Fire Danger Rating System indicates significantly higher risk and may lead to fire restrictions. Outdoor burning is not advised under a level 4 warning.
What is a Level 4 Fire?
The risk of long-distance spotting is very high with a level 4 fire danger rating. Fires spread rapidly and can increase in intensity very quickly. High-intensity burning can make these fires difficult to suppress and control.
Fire Danger Rating 5: Extreme (Red)
Level 5 represents an extreme fire danger risk. Serious restrictions are usually in place at this level and you should refrain from any outdoor burning.
What is a Level 5 Fire?
Level 5 fires spread furiously. They are fast, intense, and even the smallest of fires have the potential to become huge.
Expect erratic fire behavior and serious risk to life and property.
What is a Red Flag Warning?
A red flag warning may be present during any of the fire danger levels mentioned above. It indicates a temporary risk, with weather and fuel conditions that are ideal for the rapid and dangerous spread of fire.
Glossary of Terms Used in the National Fire Danger Rating System (NFDRS)
The NFDRS uses a number of terms that you might not be familiar with. We have tried to avoid these terms in the above definitions, ensuring that you don’t need to be familiar with the NFDRS to understand the risks, but for the sake of clarity, here’s a short list of the most common terms:
- Dead Fuels: Fuels that occur naturally and have very low moisture content.
- Duff: Dead organic matter that lies on the forest floor, underneath the freshly fallen matter.
- Fire Behavior: How a fire reacts as a result of weather and fuel conditions, as well as topography.
- Fire Danger Rating Area: The area covered by the fire danger rating system. The size of this area is based on the risk of fire, as opposed to geographical boundaries.
- Fire Weather Forecast Zone: Weather stations located within a specific zone and tasked with producing fire weather forecasts.
- Forest Litter: The “litter” is the uppermost layer of the forest floor.
- Fuel Class: A class of fuels grouped by similar characteristics.
- Fuel Moisture Content: A fuel particle’s water content.
- Fuel Models: Simulated models used to calculate fire spread based on the addition of specific fuels.
- Fuels: Organic materials that may encourage the spread of fire.
- Herbaceous Fuel Moisture: The moisture content of herbaceous plants.
- Live Fuels: Living fuels consumed by fire, including the leaves of herbaceous plants.
- Moisture of Extinction: The point at which the moisture level of a fuel source is too high for the fire to spread.
- Slash: Materials that have been left on the forest floor after logging, including branches, bark, and trees.
- Staffing Level: The level of preparedness based on staffing resources.
- Woody Fuel Moisture: The moisture content of woody vegetation.
What is Fire Spotting?
One of the terms that we did mention, and one that is very important in the spread and management of fire, is something known as “spotting”.
Spotting is when a fire produces sparks or embers that are carried to another location by the wind. Spotting means that a single fire can spread to multiple locations, turning what may otherwise be a manageable situation into an environmental disaster.
The highest levels on the fire danger rating system include a degree of spotting, but the poor fuel conditions mean it’s uncommon at lower levels.
How Are Wildfires Tackled in the USA?
Fires are suppressed by removing the resources that a fire needs to spread, including fuel and heat.
Water is applied to the fire to reduce its heat and flame retardant is applied to the ground for the same reason. Fuel is removed by clearing away vegetation and chopping down trees. Firefighters may also set small fires to burn the fuel and ensure that it doesn’t become part of a larger approaching fire.
States like California spend huge sums of money on suppression resources, but wildfires are getting big and more frequent. This is mostly down to climate change, but the general public also plays a role. Some of the most dangerous fires in recent years have been the result of accidental causes, including campfires, trash fires, and ill-conceived gender reveal parties.
Understanding the National Fire Danger Rating System will help you to avoid causing any catastrophic damage, so learn the ratings and pay close attention to the warnings.