Ministry of Forests, Lands and Natural Resource Operations - Wildfire Management Branch
Successful firefighting is based on knowing why a fire burns and what makes it spread.
If any one of these three elements is missing, there can be no fire. The basic principal of firefighting, therefore, is to remove one or more of these elements in the quickest and most effective way.
One of the most important factors affecting the behaviour of a fire is weather. The three most important components of weather are:
The stronger the wind, the faster the spread of the fire. Wind brings an additional supply of air to the fire. It flattens the flame which pre-heats the fuel ahead and causes spot fires by blowing sparks and embers ahead of the main fire into a new source of fuel.
Fuels pre-heated by the sun burn more rapidly than cold fuels. The temperature of the ground also affects the movement of air currents, as explained previously. Prolonged high temperatures also affect the endurance and efficiency of the firefighters.
Moisture in the form of water vapour is always present in the air. The measurement of that moisture is called humidity and is always expressed as a percentage.
The 'lay of the land' is called topography. This is an important factor in the rate and direction of fire spread and is usually broken into three categories:
Slope is the steepness of the land and has the greatest influence on fire behaviour.
Aspect is the direction the land faces - north, south, east or west. The aspect of a slope influences a fire's behaviour in several ways
Terrain or special land features may control wind flow in a relatively large area. Wind flows like water in a stream and will try to follow the path of least resistance.