Pakistan, July 4 -- El Nino will quickly develop into a strong event between July and September, fuelling the likelihood of extreme weather, the United Nations' weather and climate warned Friday. The World Meteorological Organisation (WMO) said El Nino had already set in, and would quickly gain strength, as it warned countries to brace for impact.

El Nino is a natural climate phenomenon that warms surface temperatures in the central and eastern equatorial Pacific Ocean, bringing worldwide changes in winds, pressure and rainfall patterns. It typically takes place every two to seven years and lasts around nine to 12 months.

Conditions oscillate between El Nino and its opposite La Nina, with neutral conditions in between.

The WMO's monthl...