El Niño and La Niña are opposite phases of a climate pattern known as the El Niño–Southern Oscillation (ENSO), which originates in the tropical Pacific Ocean and has global impacts.
What is El Niño?
El Niño, normally referred to as the warm phase of ENSO, occurs when Sea Surface Temperature (SST) in the central and eastern Pacific becomes warmer than usual. This affects global climate patterns, including rainfall and temperature distribution. The impact of El Nino on regional rainfall depends on the season and geographical location. During the June to September (JJAS) season, which is significant over the western and northern parts of IGAD, El Nino is known to cause depressed seasonal rainfall. On the other hand, it causes enhanced rainfall during the October to December season over the equatorial and eastern parts of the region. Although El Niño is generally associated with enhanced rainfall during the OND season, its impact depends on the phase of the Indian Ocean Dipole (IOD). Positive IOD is a pattern of anomalously warm SST in western Indian Ocean and cold SST in eastern Indian Ocean, as observed in 1997, 2015, and 2023, but anomalies still vary by month and location (ICPAC, 2024).
In the IGAD region, El Niño is typically associated with:
- Above-normal rainfall especially in equatorial countries like Kenya, Somalia, southern Ethiopia, and Uganda during the October-November-December season.
- For example, during the 2023 El Niño event, ICPAC predicted and observed wetter-than-normal conditions across much of the equatorial Horn of Africa. This brought relief to drought-affected areas, but also led to flash floods, displacement, and infrastructure damage, particularly in Kenya and Somalia. On the other hand, the 2015 EL Nino led to depressed JJAS rainfall and caused devastating drought in Ethiopia that affected millions of people and led to high levels of food insecurity
What is La Niña?
La Niña, which is the cool phase of ENSO, is associated with cooler-than-average waters in the eastern and central Pacific. It often results in below-normal rainfall in the equatorial eastern parts of the Greater Horn of Africa (GHA) region during the OND season and enhanced rainfall during the JJAS season and northern parts of the GHA region. Generally, but not always, La Nina is associated with a negative phase of IOD during the OND, with severe drought experienced when this combination is observed.
Highlights from the Last Three Seasonal Forecasts Issued by ICPAC
ICPAC issues rolling seasonal forecasts to guide preparedness and response across the IGAD region. Here are key insights from the most recent three forecasts for the main rainfall seasons: October–December (OND) 2024, March–May (MAM) 2025, and June–September (JJAS) 2025, developed through objective forecasting techniques.
June–September 2025 (JJAS): ICPAC forecasts a 55% probability of above-normal rainfall over central Sudan, eastern South Sudan, northern & southwestern Ethiopia, western Kenya, and eastern Uganda. Conversely, coastal Somalia and Kenya face higher chances of below-average precipitation.
- March–May 2025 (MAM): The outlook showed below-normal rainfall for Somalia, eastern & northern Kenya, and southern/northeastern Ethiopia, while parts of Tanzania, eastern Uganda, and western Ethiopia were expected to get wetter than usual.
- October–December 2024 (OND): The prediction indicated a transition to La Niña conditions, forecasting below-normal rainfall in central/southern Somalia, southern Ethiopia, and arid/semi-arid lands of Kenya.
Why It Matters for IGAD
The IGAD region is one of the most vulnerable regions to the adverse effects of Climate change. The high vulnerability of populations and systems in the region continues to worsen as the frequency and intensity of extreme events increase. Changes in ENSO phases (El Niño or La Niña) can either intensify rainfall and floods or worsen droughts. These shifts:
- Affect agriculture, water availability, and food production.
- Drive humanitarian crises due to loss of livelihoods, displacement, and disease outbreaks.
- Require timely action guided by seasonal forecasts and early warning systems.
ICPAC provides early warning information in the form of seasonal climate forecasts, advisories to help member states and partners make informed decisions. These products are critical for drought preparedness, flood mitigation, and building community resilience.
Conclusion
The impacts of El Niño and La Niña are threats to millions in the IGAD region. With evidence-based climate services from ICPAC, the region can better prepare for the seasonal extremes brought about by extreme global drivers such as El Niño and La Niña, thereby protecting livelihoods and saving lives.
References
ICPAC. (2024, April 30). Does El Niño Always Lead to Above Normal Rainfall? Examining the Short Rains in Eastern Africa during El Niño Years. From Medium: https://icpac.medium.com/does-el-nino-always-lead-to-above-normal-rainfall-651b8d0316d5
