El Niño to La Niña
When equatorial sea surface temperature is warmer than normal, this occurrence is called an El Niño, a name referring to Christmas, as El Niño often occurs around then. When equatorial sea surface temperature is cooler than normal, this occurrence is called La Nina. Both El Niño and La Niña are associated with extreme weather events.

http://sciencebulletins.amnh.org/?sid=b.v.NPP_2011.20111212&src=l