CBRN Masks · Preparedness tools

Wildfire Spread Simulator

See how fast a wildfire would spread in grass, open woodland or shrubland with wind and dry fuel, where the smoke drifts and when the fire could reach you.

Explore. Understand. Prepare.Free tools for your own location.

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Educational model, not a forecast. In an emergency, follow official alerts.How it works ↓

How to use it

  1. 1
    Place the ignitionSearch a town or postcode, click the map or use your location. With your location on, the fire starts 5 km upwind of you.
  2. 2
    Set the conditionsChoose the vegetation, wind and how dry the dead fuel is, or use today’s weather. Lower moisture and stronger wind mean a faster fire.
  3. 3
    Follow fire and smokeStep through 48 hours. The orange area is the fire, the dashed outlines show earlier edges and the grey band shows where the smoke drifts.

Wind and dryness decide how fast a fire runs.

A wildfire spreads fastest in the direction of the wind and in dry, fine fuel such as cured grass. In strong wind a grass fire can move faster than a person can run.

The model assumes flat ground, uniform vegetation and constant weather. Real fires are shaped by slopes, changing winds, firebreaks and firefighting.

How fast a wildfire spreads by vegetation and wind

Head-fire speed at 8% dead fuel moisture on flat ground, calculated with the simulator’s models. The fire front covers this distance in one hour.

Wind (10 m above ground)GrasslandOpen woodlandShrubland
10 km/h · 6.2 mph2.0 km/h · 1.2 mph1.0 km/h · 0.6 mph1.0 km/h · 0.6 mph
20 km/h · 12.4 mph4.1 km/h · 2.5 mph2.0 km/h · 1.3 mph2.0 km/h · 1.2 mph
40 km/h · 24.9 mph7.7 km/h · 4.8 mph3.8 km/h · 2.4 mph3.7 km/h · 2.3 mph

Drier fuel, slopes and gusts make fires faster; damp fuel slows them. In the simulator you can change fuel moisture and wind or use today’s weather.

Prepare before you need it

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Questions and answers

How does the wildfire simulator calculate the spread?

With published fire-behavior models: the CSIRO grassland model for grass, the same model at half speed for open woodland, and the Anderson et al. (2015) shrubland model for maquis and heath. The fire grows as an ellipse whose length-to-width ratio depends on the wind.

How fast can a wildfire spread?

In dry grass (8% fuel moisture) the model gives about 4 km/h (2.5 mph) at a 20 km/h wind and about 7.7 km/h (4.8 mph) at 40 km/h; shrubland and open woodland burn about half as fast. Under severe conditions, shrubland fires often run at around a tenth of the wind speed. The simulator shows the head-fire speed for your settings.

Does a gas mask protect against wildfire smoke?

A particle filter stops smoke particles and soot. It does not protect against carbon monoxide or a lack of oxygen close to the fire. The safest choice is to leave early when the authorities advise it.

Is the simulated fire a forecast?

No. It assumes flat ground, uniform vegetation and constant weather. “Use current local weather” takes today’s wind and estimates fuel moisture from temperature and humidity, but the weather then stays constant in the model.

How the model works · assumptions & sources

Head-fire rate of spread: grassland – CSIRO grassland model for natural, fully cured pasture (Cheney et al. 1998): R = 0.054 + 0.269U (U < 5 km/h) or 1.4 + 0.838(U − 5)^0.844 km/h, multiplied by the moisture function exp(−0.108M) for M ≤ 12% (linear above); open woodland – grassland rate × 0.5 (Cheney & Sullivan 2008); shrubland – Anderson et al. (2015): R = 5.67(0.67U)^0.91 × h^0.22 × exp(−0.076M) m/min with h = 1 m. U = 10 m open wind speed, M = dead fine fuel moisture. Fire shape: ellipse with length-to-width ratio 1.1U^0.464 (U ≥ 5 km/h) and head-to-back ratio after Alexander (1985). Smoke: wind-driven band with Briggs crosswind spread for sunny-day stability (classes A–C, depending on wind), shown for up to 6 hours. Optional current weather: wind for the hour at the ignition point from MET Norway Locationforecast 2.0 (CC BY 4.0); dead fuel moisture estimated from air temperature T (°C) and relative humidity RH (%) with McArthur’s formula (1966) as used with the CSIRO grassland model, M = 9.58 − 0.205T + 0.138RH, kept within 2–25%; the weather then stays constant. Not included: slope, terrain, spotting, build-up time, suppression.

Maps: VersaTiles, © OpenStreetMap contributors. Places and postcodes: GeoNames (CC BY 4.0). Reactor data: GeoNuclearData (ODbL 1.0, from IAEA PRIS) and the IAEA research reactor database as compiled by Wikipedia (CC BY-SA 4.0), status updated to October 2026. Current weather on request: MET Norway (CC BY 4.0). Without location permission, the starting area is estimated from the country the store detects and your browser’s time zone. City search runs in your browser; your exact location is used only with your permission and stays in this browser tab. “Use current local weather” sends the coordinates of the scenario point to MET Norway. Map tile requests reveal the viewed map area to the map provider.