El Niño is the most powerful weather event on the earth, disrupting weather patterns across half the earth's surface. Its three- to seven- year cycle brings lingering rain to some areas and severe drought to others. El Niño develops when currents in the Pacific Ocean shift, bringing warm water eastward from Australia toward Peru and Ecuador. Heat rising off warmer water shifts patterns of atmospheric pressure, interrupting the high-altitude wind currents of the jet stream and causing climate changes.

El Niño, "Christ child" or "the child" in Spanish, tends to appear in December. The phenomenon was first noted by Peruvian fishermen in the 1700s, who saw a warming of normally cold Peruvian coastal waters and a simultaneous disappearance of anchovy schools that provided their livelihood.

A recent El Niño began to develop in 1989, but significant warming...