What is la niña and what happens during la niña?

La Nina is directly opposite of El Nino, occurs when sea surface temperatures in the oceans drops than the normal levels.

Explanation:

Being a weather phenomenon the La Nina is colder as compared to the El Nino, meaning little girl. As the oceans will have lower than the average temperatures of 3 to 5 degrees. As La Nina persists for at least five months. Affecting the weather across the globe especially north America. As it is a positive and cooler phase of El Nino. In Africa, wetter than normal conditions of South Africa and Asia formation of tropical cyclones shifts westwards along the pacific ocean and south America it brings drought-like conditions to Peru and Chile.  Thus involves anomalies along the eastern Pacific, ENSO has been linked with global warming and la Nina leads to an increase in rainfall.