La Nina is a combination of oceanic and atmospheric circulation weather pattern that develops into the formation of southern oscillation system of the ENSO cycle and is a comparatively cooler system that its counterpart the El Nino meaning the little boy.
During the period of La Nina, the temperature of the pacific ocean will be normally less than 3 to 5 degrees at least for five months. Thus there are wetter conditions in Indonesia and northern brazil. In North America, this weather phenomenon brings increased rainfall across the upper middle west.
As due to this phenomenon of the La Nina can result in an intense storm in certain places and drought conditions in others as these are associated with synoptic conditions.
Due to La Nina caused catastrophic rainfall in andes it directly impacts the conditions of the Peruvian coasts and hence drought in these areas which sets the conditions of El Nino.