Fire Weather Index Map: Check Wildfire Danger for Any Location

Wildfires are intensifying globally as climate change drives hotter, drier conditions. The Fire Weather Index (FWI) is the international standard for quantifying wildfire danger from meteorological conditions. Developed by the Canadian Forest Service and adopted by fire agencies in over 30 countries, FWI translates raw weather data into an actionable danger rating. PixelGust provides FWI data for any point on Earth, making wildfire risk assessment accessible without specialized tools.

How the Fire Weather Index Works

The FWI system is a chain of six components that model fuel moisture and fire behavior from four weather inputs: temperature, relative humidity, wind speed, and 24-hour precipitation.

Fuel Moisture Codes

Three codes track moisture content at different soil depths, representing how quickly different fuel layers dry out:

• FFMC (Fine Fuel Moisture Code): Moisture of surface litter and fine fuels. Responds to weather changes within hours. Controls ignition probability.
• DMC (Duff Moisture Code): Moisture of loosely compacted organic matter. Responds over days to weeks. Affects smoldering behavior.
• DC (Drought Code): Deep organic soil moisture. Responds over months. Indicates seasonal drought severity and deep-burning potential.

Fire Behavior Indices

Two intermediate indices translate fuel moisture into fire behavior predictions:

• ISI (Initial Spread Index): Combines FFMC and wind speed to estimate how fast a fire would spread in its initial phase.
• BUI (Buildup Index): Combines DMC and DC to estimate the total fuel available for combustion.

The Final FWI

FWI combines ISI and BUI into a single numeric rating that represents the overall intensity of a potential fire. It correlates strongly with observed fire behavior: a higher FWI means faster spread, longer flame lengths, and more difficult suppression.

FWI Danger Classes

PixelGust classifies FWI values into five danger levels used by fire management agencies:

• Low (0–5): Fires unlikely to sustain themselves. Most ignitions self-extinguish.
• Moderate (5–13): Surface fires may spread in open, dry fuels. Controllable with ground resources.
• High (13–24): Fires spread quickly in most fuel types. Aerial resources may be needed for suppression.
• Very High (24–38): Aggressive fire behavior with spotting (ember transport). Structures at risk in wildland-urban interface.
• Extreme (>38): Explosive fire growth. Crown fires in forests. Conditions exceed suppression capacity.

Who Uses FWI Data?

Fire Management Agencies

National and regional fire services use daily FWI maps to position firefighting resources, issue public warnings, and decide whether to impose fire bans. In Europe, the European Forest Fire Information System (EFFIS) publishes FWI-based danger maps daily.

Insurance and Reinsurance

Wildfire is an increasingly material peril for property insurers. FWI data helps underwriters assess fire weather exposure for individual properties and portfolios. Combined with vegetation data (NDVI) and proximity to urban areas, FWI provides a weather-driven wildfire risk layer. Learn more about weather data in insurance.

Real Estate and Property Assessment

Homebuyers in fire-prone regions need to understand long-term fire weather trends. PixelGust's historical weather data reveals whether FWI conditions are worsening over time, which directly impacts climate risk for real estate.

Forestry and Land Management

Forest managers use FWI to schedule prescribed burns during moderate conditions, plan timber harvesting around high-danger periods, and assess post-fire recovery using NDVI time series to track vegetation regrowth.

Renewable Energy

Solar farm operators in fire-prone areas monitor FWI to protect installations. High FWI triggers defensive actions like vegetation clearing around panels. Wind data feeds directly into FWI, connecting two critical planning variables.

How to check FWI on PixelGust

1. Open the dashboard at pixelgust.com/app.
2. Select a location on the map, draw a polygon, or enter coordinates manually.
3. Enable the Hazards panel to view the current FWI rating and danger class.
4. View the 7-day forecast: Switch to the Forecast tab to see the predicted FWI for the upcoming week based on near-real-time GFS weather data.
5. View historical trends: Switch to Historical mode to see the average FWI over the 2015-2025 period.

Combining FWI with Other Data Layers

FWI quantifies weather-driven fire danger, but actual wildfire risk depends on multiple factors:

• Vegetation density (NDVI): Dense, dry vegetation provides fuel. Areas with high NDVI during spring that dries to low NDVI by late summer face the highest fire risk.
• Land cover type: Forests, shrublands, and grasslands burn differently. Land cover classification helps contextualize FWI severity.
• Slope and aspect: South-facing slopes (in the Northern Hemisphere) dry faster and burn with greater intensity due to higher solar radiation exposure.
• Evapotranspiration: ET data reveals vegetation water stress, which is a leading indicator of fire-susceptible conditions before FWI peaks.

Data Sources

PixelGust computes FWI using ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF). ERA5 provides hourly global weather data at approximately 31 km resolution, from which daily noon values of temperature, relative humidity, wind speed, and 24-hour precipitation are extracted. The FWI calculation follows the standard Canadian Forest Fire Weather Index System methodology as defined by Van Wagner (1987).