Extensive flooding across parts of East Africa

• Overall, the March–April seasonal rainfall performance has been largely average to above-average (110 to 200 percent of average), but with persistently below-average rainfall (60 to 90 percent of average) over the western sector of the region (southwestern parts of South Sudan, Uganda, Rwanda, and Burundi) (Figure 1). 
• Heavy El-Niño-enhanced seasonal rains in April have caused extensive flooding in parts of East Africa, with reported fatalities and population displacement in Kenya (186 fatalities), Tanzania (155 fatalities), and Burundi (29 fatalities). Parts of Uganda, Rwanda, South Sudan, Somalia, and eastern Ethiopia have also experienced some flooding in April, resulting in property, infrastructure, and crop damage. 
• Despite the damage caused by the ongoing floods, the above-average seasonal rains have largely supported significant improvement in rangeland and water resources and favorable cropping conditions in most areas. 
• Weekly Global Ensemble Forecast System (GEFS) rainfall forecasts indicate continued moderate to heavy rains with gusty winds in the region, particularly along the coastal strip, central highlands, and the western sectors of the region, elevating the risk of more flooding. 

Context: Between March and May, the following rainy seasons are underway in East Africa: Gu rains in Somalia; long rains in unimodal Uganda, Kenya, Burundi, and Rwanda; belg rains (mid-February to May) in Ethiopia, as well as the diraac/sugum rains in the northern pastoral area and gu/genna rains in the southern and southeastern pastoral areas of Ethiopia; and the first season rains in the bimodal zones of southwestern South Sudan and northern Uganda. 

The March–May seasons have had varied onsets across the region, with slow starts in March across much of the Horn and the western sector, including in Rwanda, Burundi, parts of Uganda, and bimodal South Sudan (Figure 2). In the western sector, the delayed start of the season has contributed to cumulative below-average rainfall through April. In Uganda, a timely onset in some areas was superseded by significant early seasonal rainfall deficits (between 30 to 60 percent of average) (Figure 1). Meanwhile, a timely onset was observed in the southeast and coastal areas of Kenya and the eastern parts of Tanzania. Similarly, the belg seasonal rains in Ethiopia have been largely early-to-timely, and so far, rainfall performance has been above average. The gu and diraac seasons for Ethiopia are yet to be established with a few areas of below-average rainfall in the northwest of the Somali Region.

Despite the slow seasonal start in many areas in March, increased rainfall in late March and April has resulted in cumulative above-average rainfall in many parts of the Horn through the season thus far (March 1 – April 30, 2024). In most parts of Kenya, Tanzania, and southern Somalia, the rains have been continuously above average since late March leading to severe flooding events that have reportedly claimed approximately 370 lives (155 in Tanzania, 186 in Kenya, and 29 in Burundi), displaced thousands of households, caused mudslides in Kenya, and destroyed many recently planted or standing crops. As of April 30, the risk of further flooding remains high in most parts of Kenya, northern to western Tanzania, the Somali Region in Ethiopia, and in some riverine areas in Somalia (Figure 3). 

With the observed heavy rainfall across Kenya and the Ethiopian highlands, most of the dams that cut across the Central Highlands (7 Folks Dams) in Kenya have filled, leading the government to open the spill gates. This has exacerbated flooding downstream in the eastern counties of Tana River and Garissa both of which received above-average rainfall at the start of April. Similarly, in the Juba and Shabelle regions of Somalia, high river levels with multiple open breakages have led to flooding, particularly in Middle Shabelle Region. In the Somali Region of Ethiopia, flash floods were reported in some riverine areas, notably the Shabelle Zone, and a risk of flooding remains. 

Although the heavy rains and flooding have negatively impacted some areas, much of the region has experienced the beneficial impacts of the above-average rains in April, the start of the agricultural season in many countries. In addition, vegetation and crop conditions and surface water levels generally remain favorable across the region due to the improved rainfall since the start of April, coupled with a favorable October-December 2023 rainy season (Figure 4).

The GEFS rainfall outlook for the next two weeks, May 9 to 23, is indicative of moderate to locally heavy rainfall across the region. This is likely to continue until the end of the month, as depicted in Figure 5. Flood risks remain over the central highlands of Kenya and its environs. The flood-prone regions of southwestern Ethiopia, southern Somalia, eastern DRC, and neighboring eastern Rwanda, Burundi, and parts of Uganda are also at flood risk in the next two weeks.

Typically, the seasonal rains are likely to intensify and peak in late May for much of the East Africa coastal strip, Somalia, and the south-east Ethiopia regions, sustaining the elevated flood risk.

Overall, cropping and rangeland conditions are likely to continue replenishing and remain favorable, except for flood-affected regions during this period.