Surface wind speed is often the most critical weather element effecting fire behavior and fire danger. It is also the most variable and consequently the hardest to evaluate.
Air moving across the surface of the land constantly changes in both speed and direction.
Over a period of time, one observes a series of gusts and lulls in the wind speed. Winds that persist for 1 minute can effect gross fire behavior, including rate of spread and fireline intensity. Momentary gusts on the other hand have little effect on the overall rate of spread or intensity. However, they can produce large, temporary fluctuations in flame height and can easily trigger crowning or throw showers of embers across the fireline. These standards are fine for fire danger rating but often cause confusion for firefighters on the ground.