Global Fires : Image of the Day from NASA Earth Observatory:

Like plants, fire activity grows and wanes in seasonal patterns. Globally, fires peak in July, August, and September, when summer’s drying heat makes vegetation flammable and lightning ignites the landscape. In addition, summer is the time when many crops are harvested and fields are burned in the Northern Hemisphere, where most of Earth’s continents are. On any given day in July, August, or September an estimated 6,000 fires burn across the world. February is the slowest month of the year, with an estimated 3,000 fires per day. To watch fires move across the globe throughout the year, see Fire in the Global Maps section of the Earth Observatory.

The contrast between the two months is shown in this pair of images made from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. The top image shows all of the fires detected during August 2008, while the lower image shows February 2008. Dense fire concentrations are yellow, while more scattered fires are red. February is clearly the burning season in the tropics. A solid band of red stretches across the Sahel of Africa, and hundreds fires were burning in northern South America, Central America, and southeast Asia. In August, the fire regions shifted into more temperate regions north and south of the Equator. Intense agricultural fires burn in south-central Europe and in southern Africa.

An animation of global fires is available on the Global Maps section of the NASA Earth Observatory