Fire - Wildfire Spread Simulation

The Fire kit simulates wildfire spread across a selected area. Draw an area or select an existing shape, choose the ignition source, and set the wind and fuel dryness. Use the time slider to view the simulated spread.

The simulation is calculated on Scribble Maps servers using three inputs:

• Terrain: Scribble Maps elevation, 1 m lidar across most of the US. Fire spreads faster uphill.
• Fuels: what is on the ground and in the canopy. In the US this is LANDFIRE: the fuel type (grass, shrub, timber litter and so on) and the tree canopy for every 30 m. In Canada it is Natural Resources Canada's national fuel type map, also 30 m: the forest types Canadian fire agencies use, such as boreal spruce, jack pine, aspen, mixedwood and grass.
• Weather: in the US the kit starts from the National Weather Service forecast wind for your area; elsewhere from a steady 20 km/h west wind. You can change the wind and choose how dry the fuels are.

The simulation uses the fire behaviour models for each country. In the US: Rothermel surface fire, with Van Wagner and Rothermel crown fire, the same science behind the US Forest Service's FARSITE and FlamMap. In Canada: the Canadian Forest Fire Behaviour Prediction (FBP) System, the model Canadian fire agencies use.

Fire works in the United States and Canada. An area that crosses the border uses each country's data and model on its own side.

Account requirements and area limit

Note: Fire is a Pro Business kit. Every signed-in account also gets 3 free fire analyses to try it. Preparing an area uses one. Changing the wind, the dryness, the start of the fire or the time never uses one. A run that fails does not use one. The kit shows how many free analyses you have left.

To learn how to upgrade, see How to upgrade to a Pro account.

An area can be up to 50,000 acres (about 200 square kilometres).

Open the Fire kit

There are two options for opening the kit:

• Option 1: Click Kits at the bottom-right of the map, then select Fire.
• Option 2: Open Maps & Data, select the Kits tab, then find Fire and click Use Kit.

You can also right-click a polygon, rectangle or circle on your map and choose Simulate fire. The kit opens with that shape as the area.

Choose the area

• Use selected shape: opens a list of the areas on your map. Click one, or click Select on map and then click the shape on the map.
• Draw area: click the map to outline the area, then click the first point to finish.

Simulate a fire

1. Click Create layer. The kit reads the terrain and fuels for the area once. The first time, it asks you to confirm that you understand this is a simulation and will not use it to decide whether to evacuate.
2. Choose where the fire starts in Fire starts:
   • Across the edge (upwind): fire comes into the area across its windward edge, as a fire burning toward a neighbourhood would.
   • A marker you pick: the fire starts at a marker, such as a lightning strike, a campfire or a vehicle fire. Pick the marker from the list, or click Select on map and click it.
   • Along a line you pick: the fire starts along a line, such as a power line or a road edge.
   • From a fire's edge (an area you pick): for a fire that is already burning. Draw or pick its current perimeter as a polygon, rectangle or circle, and the fire grows outward from it.
3. Set Wind from (the direction the wind blows from), Wind speed and Fuel dryness (Extreme, Very dry, Dry or Moderate). In the US the wind starts as today's National Weather Service forecast for the area; the kit says so under the controls until you change it.
4. Drag the Hours since ignition slider. Every run covers 48 hours: the first half of the slider is the first 12 hours, the second half the rest. The burned area on the map and the numbers change as you move it. The report card on the map has its own slider, so you can watch the fire from the map even with the kit closed.

Each change of the fire's start, wind or dryness is simulated again in about a second. Moving the time slider is instant. If you change the area's shape after Create layer, click Create layer again to simulate the new shape.

Only ground that can burn does: roads, water, rock and most farm fields stop the fire, and a fire burning across a narrow road can still be stopped by it.

In Canada, the dryness levels are set as fire weather codes (from Moderate to Extreme), and aspen and mixedwood burn as leafless in spring and fall and green in summer, by today's date.

Read the results

The colours on the map show how the fire burns:

• Fire front (yellow): where the fire has just arrived.
• Flames under 1.2 m to Flames over 3.4 m (orange to dark red): the flame length at the fire's head. Flames over 1.2 m are too intense for firefighters with hand tools; over 3.4 m, crowning and spotting are likely.
• Crown fire (dark purple): the fire burns through the tree canopy.

The report displays the following values:

• Burned: the area burned so far, and its share of your area.
• Fastest spread: the fastest the fire's head moves anywhere in the area.
• Longest flames and Crown fire: how intense the fire gets.

Under Create layer (and on the card) the kit displays fuel data coverage and confidence for the area.

Simulation limitations

This is a planning estimate, not a fire forecast. It does not model:

• embers carried ahead of the fire that start new spot fires,
• firefighting, fire breaks being built, or aircraft,
• the wind or weather changing during the fire.

Note: Real fires can move much faster than this, especially with spotting. Never use it to decide whether to evacuate. For an active fire, follow your local emergency services.

We test it against real fires. Replaying more than 200 twelve-hour periods of real wildfires, the kit's pace in the US was close to the real fires on average, and in Canada it ran about 3 times faster, because it keeps the afternoon fire weather for every hour. To see the results, how we test the model, what it leaves out and how far to trust a result, read How accurate is the Fire kit?

Save and manage the results

Results are added to a Fire folder on your map, with a subfolder for each area and run. The burned area is an image layer and the report card keeps the numbers. You can save, share and undo these layers like other map objects. When you save the map, the fire is saved as it is at that moment.

Data sources

• Fuels and canopy (US): LANDFIRE (U.S. Department of the Interior, U.S. Geological Survey, and U.S. Department of Agriculture), 30 m.
• Fuel types (Canada): Canadian Forest Fire Danger Rating System Fire Behaviour Prediction Fuel Types 2024 (Natural Resources Canada, Canadian Forest Service), 30 m, Open Government Licence - Canada.
• Terrain: Scribble Maps elevation: USGS 3DEP 1 m lidar across most of the US, 30 m elsewhere.

Ask Scribble

To run an analysis with Scribble, enter a request such as:

• "How would a fire spread across this area with a 30 km/h west wind?"
• "Start a fire at this marker and run it for 6 hours on a very dry day."
• "What if a fire started along my power line?" (Scribble finds the line by its name on your map.)
• "Grow the Creek Fire perimeter outward for 12 hours with tomorrow's wind." (Scribble uses the polygon with that name as the fire's edge.)

To get help choosing a kit, click Kits, then Not sure what to use? Ask AI, and describe what you need to do.

See also

• How accurate is the Fire kit?