El Nino and La Nina

The El Nino phenomenon is caused by the uneven heating of ocean waters, while La Nina is caused by a band of uneven cooling. Both of these bands originate off the coast of Ecuador and Peru. These bands occur regularly, with El Nino happening about every 3-7 years but lasting only 9-12 months. The La Nina band develops afterwards and lasts longer, often 2-3 years. An El Nino year brings us a wetter winter and a La Nina year gives us drier winters. These are natural climate patterns which bring us weather.