The 2009 Southeast Asian haze was an episode of large scale air pollution primarily caused by slash and burn practices used to clear land for agricultural purposes in Sumatra, Indonesia. It affected the areas surrounding the Straits of Malacca which besides Indonesia include Malaysia and Singapore. The haze began in early June 2009 and progressively became worse toward July. With a prevailing dry season caused by El Nino, burning and hence the haze was expected to continue until August or September when the monsoon season arrived.