Natural England - Fire Severity
Fire Severity
The Met Office Fire Severity Index
Where the relevant authority has given an outline direction for fire prevention reasons, exclusion of the public will only happen where the FSI reaches exceptional (level 5).
The Met Office Fire Severity Index is an assessment of the current day's fire severity and a forecast of the fire severity over the coming five days. The index values are from 1 to 5, which represents an increasing degree of fire severity where:
= very low fire severity
= low fire severity
= moderate fire severity
= high fire severity
= exceptional fire severity
The fire severity index maps displays the index on 10km x 10km squares over the whole of England and they are updated every day.
Please note that the quality of the forecast fire severity index for 5 days ahead will not be as accurate as the fire severity index for today. This is because there are always uncertainties in weather forecasting several days ahead.
How is it calculated?
The index uses information such as wind speed, temperature, time of year and rainfall to produce a fire severity assessment. This weather information is derived from the myriad of observations taken around the country by the Met Office every hour. To produce forecasts of fire severity, weather information from the Met Office operational forecast model is used.
How was it developed?
The Met Office Fire Severity Index was chosen after comparing the performance of a number of methods used worldwide for identifying fire risk. It is based on a similar approach to the Canadian model, which is also used in other parts of the world. It was also the best at identifying periods of high fire severity, such as those present in 1976 and in the spring of 2003, without producing a significant number of false alerts.
The index was tested by comparing it against observations of fire severity taken throughout England and Wales during 2003. Alongside being the most the most accurate index tested, we selected it because it can be used to produce forecasts over the coming days and because it uses a physical approach to identifying fire severity, rather than a statistical approach.
How can I find out more information?
Read a copy of the Met Office Fire Index Report 
. We also have supplementary Met Office reports in our related articles section on this page.
