What is it called when a fire burns perpendicular to the wind?

When a fire burns perpendicular to the wind, it is known as a flank fire. This type of fire behavior occurs when flames spread parallel to the direction of wind at the flanks of the fire. Since the wind is blowing in a direction and the fire is spreading perpendicular to that direction, it results in a relatively slower spread compared to a head fire, which moves with the wind. Understanding this concept is crucial for fire management and control strategies since different fire behaviors require different tactical responses.

In contrast, a backfire burns against the wind, providing a way to control the fire’s spread. A spot fire refers to an isolated ignited area, typically resulting from embers being carried by the wind, while a head fire moves with the wind and often presents the fastest and most dangerous fire spread.