Seasonal (3-month) sea surface temperatures in the central tropical Pacific Ocean compared to the 1981-2010 average. Warming or cooling of the ocean surface near the International Dateline is one of the criteria used to monitor the El Niño-La Niña climate pattern. Data from NOAA CPC.
Difference from average sea surface temperature across the tropical Pacific Ocean during a strong El Niño (top) and a strong La Niña (bottom). During El Niño, the east-central tropical Pacific is warmer than average. During La Niña, the region is colder than average. Data from NOAA NCEI.