Fire Severity Index (FSI)

The Fire Severity Index (FSI), is an assessment of how severe a fire could become if one were to start. It is based on several different criteria to determine the present and future short-term risk. These include:-

  • Time of year – school holidays and summer etc. are a bigger risk. 
  • Vegetation condition – dead or dying, fresh new growth etc. as this makes a difference to the combustibility of the material. 
  • Temperature. 
  • Precipitation 
  • Wind

The FSI shows the current day's fire severity and a forecast of likely fire severity over the coming days.

  • Low fire severity – likelihood of fire low. 
  • Moderate fire severity – People should take care with any fire/BBQs etc. 
  • High fire severity – People should not use any open fires/BBQs etc and ensure that any smoking materials are disposed of responsibly 
  • Extreme fire severity – As above but even more care should be taken.


Members of the public to remain vigilant during the High and Extreme levels and follow any local guidance provided by the Forestry Commission and the Fire Service.