The drier the air, the more intense the bush fire since fires rely on oxygen. During dry weather, plants contain less moisture and hence more oxygen allowing them to burn more readily. Because weather conditions can change rapidly, bush walkers who plan camping trips should be aware that with hot, dry, windy conditions, fire danger levels may rise from medium to high or even extreme within one or two weeks during dry periods. This of course depends on the area. Some areas such as those that are elevated dry out quicker than valley areas.
Fires can begin when sunlight is focused to a point by broken glass onto dry leaves or glass.
However, fires are often accidentally or deliberately lit by humans. Lightning is also a cause of fires. Regardless of the cause, fires can spread and move quickly through a forest with strong, dry winds. Even though bush fires are easily recognised, many people who do not take an interest in observing the weather also do not anticipate fires regardless of the conditions. Because fires normally rise, they can progress more rapidly vertically than downward.