WMO Forecasts Wetter Conditions in Southern US and Eastern Africa, Raising Flood Risk

The other side of El Niño's rainfall dipole

El Niño does not simply remove rain from the tropics; it rearranges it. The World Meteorological Organization's September 2026 update describes rainfall patterns showing a pronounced atmospheric response to a strong Pacific El Niño, with wetter-than-average conditions expected in parts of eastern Africa, southern Brazil and the southern United States.

BBC reporting aligned with the WMO outlook notes that these regions face raised chances of flooding as the event intensifies towards its late-2026 peak. The hazard is not uniform — local topography, urban drainage and soil saturation determine whether extra rainfall becomes manageable or catastrophic.

Peru, Ecuador and parts of Brazil have previously experienced increased rainfall during strong El Niño episodes, producing flash flooding and landslides particularly in urban centres where water cannot drain quickly.

Southern United States on alert

For the southern United States, El Niño winters and adjacent seasons often bring above-normal precipitation, particularly along the Gulf Coast and parts of the Southeast. Emergency managers monitor that signal because saturated ground from one storm system leaves communities vulnerable when the next arrives.

WMO's multi-model forecasts for September through November 2026 also indicate above-normal temperatures across almost all land areas, meaning flood events may coincide with heat stress that complicates response and recovery. Combined with long-term warming, the agency warns that impacts may be more intense than during previous El Niño events of comparable ocean strength.

Federal and state agencies have been reviewing dam safety, levee maintenance and flood insurance uptake in high-risk counties, according to reporting tied to the September forecast release.

Eastern Africa's dual exposure

Eastern Africa occupies a complex position in El Niño geography. Some subregions receive enhanced rainfall that supports pasture recovery after drought; others face flash floods that destroy crops, contaminate water supplies and displace populations. The Greater Horn has historically seen both patterns within a single El Niño cycle depending on timing and interaction with the Indian Ocean Dipole.

Humanitarian agencies are particularly alert to water-borne disease outbreaks — cholera and other diarrhoeal illnesses — that often follow flooding in areas with limited sanitation infrastructure. WMO's coordination with health partners is aimed at translating seasonal rainfall outlooks into pre-positioned medical and water-treatment supplies.

Forecast confidence and preparedness windows

WMO assigns high confidence to the persistence of El Niño through February 2027, giving flood-prone regions a multi-month window to prepare. Recommended measures include clearing drainage channels, updating contingency plans for agriculture and public health, and communicating seasonal outlooks to communities that may not distinguish a probabilistic forecast from a certain outcome.

Wilfran Moufouma Okia, head of climate prediction services at WMO, has noted that global average temperatures typically receive a temporary boost after strong El Niño events, with implications that extend into 2027 even as rainfall patterns shift season by season.