It is the latest occurrence of the Southeast Asian haze, a long-term issue that occurs in varying intensity during every dry season in the region. It has mainly been caused by forest fires resulting from illegal slash-and-burn practices, principally on the Indonesian islands of Sumatra and Kalimantan, which then spread quickly in the dry season, prolonged by the formation of Typhoon Francisco in the Pacific, and the low-pressure system forming in the South China Sea, and Pacific Ocean.[2]