Learn to read Fire Danger levels — stay away from wildfires

With the warm Northern Hemisphere season upon us, look out for Fire Danger levels as you head outdoors for hiking, mountain biking, and other activities to stay away from wildfires. This article will tell you what it is and how to read it.

What are Fire Danger levels?

Fire danger as a warning system is a multi-level system that shows how dangerous forests and other out-of-town areas are in terms of fires right now, and also gives a forecast for the future.

The system takes into account several major constant and variable factors that affect the ease of occurrence, spread, and control of wildfires by the appropriate services — the various national government meteorological and forestry agencies. These include current and preceding (to the fire) weather, type of fuel (trees, bushes, grass...) — susceptible to burning, including how wet or dry it is, and more.

In particular, all three main weather elements — air temperature, precipitation (or rather lack of it), wind direction, speed, and gusts — influence the occurrence of wildfires. They also determine how quickly a fire will end naturally.
Among other basic weather elements, fires are also influenced by the relative humidity of the air. When humidity is low, the air draws moisture from trees and other fuels, and when humidity is high, the opposite is true. In other words, when it drops, wildfires increase because thin fuels such as grass and conifer needles become drier. This is less critical for the trees themselves. But the intensity of tree trunk burning can be significantly affected by several heavy rains in a row.
Other phenomena are primarily lightning occurring during strong thunderstorms and storms of various types, but also, for example, during volcanic eruptions.

The second main and also very frequent cause of forest fires is careless handling of fire while outdoors.

Accordingly, when you go hiking and camping in the mountains or for other outdoor activities, you should be equally careful with wildfires to avoid becoming its reason and know the Fire Danger levels so as not to become a victim of it.

Brian Wangenheim / Unsplash

How to read Fire Danger levels?

Unlike some other meteorological and natural systems, for high UV or geomagnetic storm warnings, fire danger, has no one exact name worldwide, it may be called Fire Danger Levels, Fire Danger Rating, Fire Danger Index, Fire Danger Forecast, and the like depending on the source.

For example, in the US, the Department of Agriculture Forest Service, has been issuing National Fire Danger Rating (NFDRS) warnings since 1974. In Canada it is the Canadian Forest Fire Weather Index (CFFWI), in South Africa — the Fire Danger Index (SAFDI), in Australia — the McArthur Forest Fire Danger Index (FFDI) named after the scientist who introduced it in the country.

In Europe, including France and other countries, after many years of testing various indices, they have adopted the Canadian index as the main one. There are also local scales like the Alpine Forest Fire Warning System, which, as its name implies, operates in the Alps. For example, in Italy these are the administrative regions of Piedmont, Lombardy, Trentino, Veneto, and Venezia Friulia-Giulia.

Let’s further explain how to read such a levels using the National Fire Danger Rating (NFDRS) in the United States as an example. The NFDRS is a simple warning system of five numbered and color-coded levels, and recommendations for behavior during a wildfire based on each level:

Low Fire Danger — 1 (Green)

Wildfire probability: Fire starts are unlikely.
Weather and fuel conditions: Weather and fuel conditions will lead to slow fire spread, low intensity, and relatively easy control with light mop up.
Outdoor burning: Controlled burns can usually be executed with reasonable safety.

Moderate Fire Danger — 2 (Blue)

Wildfires probability: Some wildfires may be expected
Weather and fuel conditions: Expect moderate flame length and rate of spread. Control is usually not difficult and light to moderate mop up can be expected.
Outdoor burning: Although controlled burning can be done without creating a hazard, routine caution should be taken.

High Fire Danger — 3 (Yellow)

Wildfires probability: Wildfires are likely
Weather and fuel conditions: Fires in heavy, continuous fuel, such as mature grassland, weed fields, and forest litter, will be difficult to control under windy conditions. Control through direct attack may be difficult but possible, and mop up will be required.
Outdoor burning: Outdoor burning should be restricted to early morning and late evening hours.

Very High Fire Danger — 4 (Orange)

Wildfire probability: Fires start easily from all causes and may spread faster than suppression resources can travel.
Weather and fuel conditions: Flame lengths will be long with high intensity, making control very difficult. Both suppression and mop up will require an extended and very thorough effort.
Outdoor burning: Outdoor burning is not recommended.

Extreme Fire Danger — 5 (Red)

Wildfires probability: Fires will start and spread rapidly.
Weather and fuel conditions: Every fire start has the potential to become large. Expect extreme, erratic fire behavior.
Outdoor burning: NO OUTDOOR BURNING SHOULD TAKE PLACE IN AREAS WITH EXTREME FIRE DANGER.

Indices in other countries use more or less the same, in which, however, there may be some differences. For example, the McArthur Forest Fire Danger Index (FFDI) in Austria, a country particularly prone to fires because of its large areas of dry forest and high temperatures, combines Low and Moderate levels into one, with Severe level between Very High and Extreme, and Catastrophic levels as the most dangerous. The index also uses an expanded numeric scale: 0–11 for Low level, 12–31 for High level, 32–49 for Very high level, and so on, which means there is some difference between Low 0 and 11.

Where to get Fire Danger forecast?

Firstly, you can find out about Fire Danger levels in your home region or a country or the ones you are going to travel on the official websites and applications of the relevant meteorological and other services via the links above. They also publish so-called 'fire danger maps' (e.g. for Europe), on which the fire-hazardous regions are marked by color, which is very convenient.

Secondly, you can also track the likelihood of wildfires starting, spreading, and stopping on your own with apps like Windy.app. In particular, in the app you will find the following features useful:

1. Interactive Weather Map. It contains wind and precipitation layers from different weather models. For the US, choose regional NAM or HRRR — they predict the weather more accurately for the region then global models such as an American GFS.

Weather Map in the Windy.app for iOS

2. Relative Humidity Forecast. In the app for the same US, you can find it in the same GFS model or add it to your custom weather profile. There are profiles for mountain biking, paragliding, as well as for travel in general (Lite profile).

Relative humidity in the Windy.app for iOS

3. Nearest Weather Stations to the Spot. It allows you yo compare the forecast data with the real situation in the atmosphere, including wind and air temperature. Activate also the Live Weather Stations feature on the Weather Map.

Weather stations in the Windy.app for iOS

4. ECMWF-ENS Weather Model. With it, you can compare wind and temperature forecasts by the ECMWF model running more than 50 times on one chart. This will help you understand how much you can trust the forecast.

ECMWF-ENS in the Windy.app for iOS

5. Weather History. For longer time periods, use it to find out what the weather in your region was like in the previous 10 years accurate to the day. Usually, fires occur in the same places on a regular basis. The archive also includes wind, precipitation, and day and night temperatures.

Weather history in the Windy.app for iOS

Finally, you can see the current Fire Danger level directly on the spot — like on the photo in this article. Even if you forget to check the forecast, it will help you to be more careful during your active recreation, move it to another place or postpone it for your safety.

Text: Ivan Kuznetsov

Cover photo: Brian Wangenheim / Unsplash