El Niño has arrived when temperatures in the eastern Pacific Ocean along the equator west of South America warm by at least half a degree Celsius (0.9 Fahrenheit) above normal

The last reversal was about 780,000 years ago. Reversals are not instantaneous; they happen over a period of hundreds to thousands of years, though recent research indicates that at least one reversal could have taken place over a period of one year.

29,031.7 feet or 8,848.86 meters

La Niña has arrived when temperatures in the eastern Pacific Ocean along the equator west of South America cool by at least half a degree Celsius (0.9 Fahrenheit) below normal