Deadly flooding has replaced the dry start to the 2014-2015 southern Africa monsoon, and the wet season has several months left go.

Millions of people in southern Africa depend on monsoon rains that begin around November and last until March or April. If the monsoon is erratic, millions of people can suffer. So far in 2014-2015, the monsoon in southeastern Africa has been anything but normal.

Devastating floods across Malaysia and Thailand in late December and mid-January bear the hallmarks of an enhanced MJO climate pattern superimposed on the seasonal monsoon.

During the second half of December and the beginning of January, places from Sri Lanka to northwest Australia experienced exceptionally heavy rains, flash floods, and landslides.

Near the Earth’s equator, solar heating is intense year round. Converging trade winds and abundant water vapor all combine to produce a persistent belt of daily showers known as the Intertropical Convergence Zone.

In May and June each year, speculation about the coming of the monsoon fills newspapers and conversations across India. Everyone is concerned about if, when, and how much rain will arrive. But none have more at stake than India’s over 100 million farming households.

One of ENSO’s most important influences is to the Indian Monsoon—the large-scale circulation pattern that brings the Indian subcontinent the vast majority of its yearly rainfall. And while La Niñas tend to increase monsoon rainfall, the monsoon’s relationship with El Niño can be a little more complicated.  

A 2011 NOAA research paper that tied weaker South Asian summer monsoons to human activities has won the World Meteorological Organization’s Norbert Gerbier-MUMM International Award for 2013.