la nina is just the opposite part of the cycle from the more famous el nino.

"The El Niño–Southern Oscillation is a single climate phenomenon that periodically fluctuates between three phases: Neutral, La Niña or El Niño.[4] La Niña and El Niño are opposite phases which require certain changes to take place in both the ocean and the atmosphere before an event is declared... During the development of El Niño, rainfall develops between September–November.[1] The cool phase of ENSO is Spanish: La Niña, lit. 'The Girl', with SSTs in the eastern Pacific below average, and air pressure high in the eastern Pacific and low in the western Pacific. The ENSO cycle, including both El Niño and La Niña, causes global changes in temperature and rainfall."