The El Nino warming the Pacific Ocean since June has peaked, but is expected to influence climate patterns worldwide up to mid-year before dying out, according to the World Meteorological Organization (WMO). However, the United Nations agency said that forecasting uncertainties meant it could not rule out the possibility that El Nino would persist beyond mid-year. El Nino, driven by an abnormal warming of the eastern Pacific Ocean, can create havoc in weather patterns across the Asia-Pacific region, unleashing droughts in some places and heavy storms in others. It typically lasts from 9 to 12 months. The most likely scenario is for sea surface temperatures across the tropical Pacific, which rose by 1.5 degrees Celsius at its peak last November-December, to return to normal by mid-2010, WMO said in a statement. The WMO said that the current El Nino, which can occur every two-seven years, was of a moderate level, "close to or slightly above the typical strength seen in the historical record of El Nino events".