El Niño affects the weather in large parts of the world. The effects depend strongly on the location and the season. We have studied the HadCRUT2 analyses of sea surface temperature and 2-meter temperature over land with at least 35 years of data, and investigated how these observations correlate with the Niño3.4 index that describes the strength of El Niño and La Niña.

The colours encode the strength of the relationship with El Niño and La Niña. Red areas are almost always warmer during El Niña and colder during La Niña. In the dark orange areas El Niño determines about half the variability, in the liht orange areas one quarter. In the dark green areas it is often colder during El Niño or warmer during La Niña. In North America the effect is non-linear.