La Niña, Spanish for "the little girl," is also called a cold episode, "El Viejo" (The Old Man), or anti-El Niño. It is one of two major changes in the Pacific Ocean surface temperature that affect global weather patterns. La Niña and El Niño ("the little boy") are the extreme phases of the El Niño/Southern Oscillation, a climate cycle that occurs naturally in the eastern tropical Pacific Ocean. The effects of both phases are usually strongest from December to March. In some ways, La Niñais the opposite of El Niño. For example, La Niña usually brings more rain to Australia and Indonesia, areas that are susceptible to drought during El Niño.

La Niña is characterized by unusually cold ocean surface temperatures in the equatorial region. Ordinarily, the sea surface...