Pakistan, Oct. 8 -- El Nino is expected to strengthen further before reaching its peak in December, the United Nations said Thursday. The World Meteorological Organisation (WMO) warned the event could become one of the strongest since 1950.

The weather phenomenon is likely to raise temperatures across much of the world. It could also change rainfall patterns and increase risks of drought and flooding. The WMO said these effects may add pressure to climate impacts caused by human activity.

El Nino develops when surface waters become warmer in the central and eastern equatorial Pacific Ocean. This warming can alter global wind, pressure and rainfall patterns. The phenomenon usually occurs every two to seven years and lasts about nine to 1...