The FWI (Fire Weather Index) is a Canadian system adopted internationally that assesses fire danger from weather data. It integrates 6 components: Fine Fuel Moisture Code (FFMC), Duff Moisture Code (DMC), Drought Code (DC), Initial Spread Index (ISI), Build-Up Index (BUI), and the final FWI.
In Spain
AEMET calculates FWI daily and publishes it as a fire risk index at 5 levels (low to extreme). Highest values occur in summer with dry winds (cierzo, tramontana, Santa Ana), low humidity, and high temperature. An extreme FWI triggers access restrictions to forests and preventive deployment of firefighting resources.