ENSO per country forecasting·
Seasonal rainfall outlooks, ENSO and IOD tracking, and past-season rainfall impacts for One Acre Fund countries.
Normally the trade winds push warm surface water westwards across the Pacific, piling it up near Indonesia. Every few years those winds weaken, the warm water slides back east and settles off South America. That is El Niño. La Niña is the same thing in reverse: stronger winds, colder water in the east.
2026 was a particularly interesting case. In early April a rare triplet of tropical cyclones spun up in the western Pacific, one north of the equator and two south of it. Their combined circulation drove a burst of westerly wind along the equator that reversed the trade winds and pushed warm water east. Niño 3.4 went from +0.26 °C on 8 April to +0.97 °C three weeks later, and the westerlies were running harder than the ones that preceded the 1997–98 super El Niño (Source 1). By late spring, forecasters were already putting the odds on a strong-to-historic event (Source 2).
This matters to us at One Acre Fund because a warmer Pacific changes tropical rainfall patterns around the world. The knock-on effects reach East and Southern Africa several months later.
To make this phenomenon measurable, scientists use average sea-surface temperature over one fixed rectangle in the central Pacific Ocean: 5°N to 5°S, 170°W to 120°W. That rectangle is called Niño 3.4. The temperature quoted everywhere is the anomaly, meaning how far the average sea-surface temperature in that rectangle sits above or below normal, in Celsius. Above +0.5 °C is El Niño, below −0.5 °C is La Niña, and about +1.5 °C upwards is a strong event.
The Indian Ocean runs its own, smaller version of El Niño. The Dipole Mode Index (DMI) is simply the temperature difference between the Western Indian Ocean, off East Africa, and the Eastern Indian Ocean, off Indonesia.
A positive IOD means the West is unusually warm. Warm water evaporates, so there is more moisture in the air moving inland over East Africa, creating heavier than normal rainfall.
The IOD normally only runs from about June to November and peaks around September to November, which lands squarely on the October-November-December (OND) period, or short rains in Kenya. That timing is the reason it matters so much in East Africa and much less in Southern Africa, where growing seasons start later.
OND is October, November,
December. MAM is March, April, May. DJF is December,
January, February. JAS is July, August, September.IRI Multi-Model Probability Forecast for Precipitation, rendered per One Acre Fund country.
One Acre Fund country. The map zooms to its growing areas; the ENSO & locust tabs are global (the same for every country).
Show the rainfall outlook or the temperature outlook.
Colours show the chance the season lands in the wettest, middle, or driest third of the 1991–2020 record (for temperature: coolest / middle / warmest). Deeper colour = more confident; white = no clear signal. Green outline = OAF growing areas.iOAF — One Acre Fund. AEZ — agro-ecological zone (areas with similar climate & soils). Tercile — one of three equal thirds (driest / middle / wettest) of the 1991–2020 record.
IOD watch → week-by-week tracking of the two boxes the index is made of, model outlooks from BoM and IRI, and this year against 2019. In-depth.
All 10 OAF countries. Rainfall is averaged over the OAF growing areas where farmer locations are loaded, otherwise over the whole country. DRC is the exception: OAF works in the western strip (Kongo Central), so it is clipped to that region rather than averaged across the Congo basin.
Each country's actual growing season(s).
The map shows the average rainfall anomaly across those years.
Composite = the phase average. Or pick one season (or click a bar below) to see just that season's map. Each entry reads season months · the ENSO event and its peak strength; the full story is in the headline and the bar tooltips. Seasons that cross the new year are keyed like 2023/24, so a DJF row is never mistaken for calendar 2024. To hunt for past analogues, use the filter chips under the chart rather than this list.