Explainer: How wildfire starts and spread; all you need to know

Hot summer days increase the risk that wildfires will ignite or spread. Over the last few years, there’s been a global increase in the frequency and severity of such fires.

Wildfire is an uncontrolled fire in an area of combustible vegetation that occurs in the countryside or a wilderness.

Wildfires require three things to ignite and eventually spread: fuel, heat and oxygen (commonly referred to as the fire triangle).

The composition of fuel (trees or vegetation in an area) influences how quickly a fire will spread.

How fast and far wildfires spread depends on three factors: fuel, weather and topography (collectively known as the fire behavior triangle).

Heat always rises. This makes steep slopes a risky area for wildfires. If a fire ignites at the bottom of a slope, the hot air rises and begins to preheat the trees above making them ready to ignite once the fire reaches them.

Elevation and direction of the slope also affect how fast wildfire spreads.

Wind supplies fire with additional oxygen. It also causes embers to move across a landscape at a faster rate.

More than 36 percent of India’s forest cover has been estimated to be prone to frequent forest fires.