Drought prediction is more successful in some regions than others. It depends on how strongly these regions are influenced by large-scale climate phenomena, such as El Niño and La Niña, the two extremes of the El Niño Southern Oscillation (ENSO) in the Pacific. As far as the United States is concerned, El Niño (warming) or La Niña (cooling) events in the equatorial East Pacific Ocean increase the possibility of wet or dry years in coastal regions. El Niño does not appear to have as much drought impact in the central parts of the United States, but some La Niña events have been associated with historic droughts there.

The Climate Prediction Center's monthly El Niño/Southern Oscillation (ENSO) discussion outlines the current status and expected future development of tropical Pacific conditions, the waxing and waning of El Niño or La Niña events and the neutral periods in between. There is a more general discussion of current conditions on their web site. It also provides historical information about previous El Niño and La Niña events and their relations to U.S. climate.

The National Drought Mitigation Center discusses the factors that go into predicting drought and specifically the connection between El Niño and drought.

NOAA's Climate Prediction Center monitors several global climate phenomena that can help predict drought and other weather extremes, such as El Niño/La Niña, the Madden/Julian Oscillation, atmospheric tele-connections, and blocking.

The Center for Research on the Changing Earth System studies decadal climate variability, looking at long-term fluctuations. The Centers web site discusses the Dust Bowl as an example of an event caused by decadal climate variability.

The Climate Impacts Group at the University of Washington provides guidance on how to incorporate the effects of the El Niño/La Niña forecasts into operational decision support systems.