The formula to calculate the Fire Weather Index (FWI) is:
FWI=0.434⋅ln(ISI)+0.537⋅ln(BUI)−1.233
Where:
Let's say the Initial Spread Index (ISI) is 10, and the Buildup Index (BUI) is 20. Using the formula:
FWI=0.434⋅ln(10)+0.537⋅ln(20)−1.233
We get:
FWI≈1.38
So, the Fire Weather Index is approximately 1.38