Why Lagos, Accra and Nairobi flood so fast
A single tropical downpour can turn roads into rivers within an hour. The causes are as much about the city as the sky.
Published October 12, 2026
A single tropical downpour can turn roads into rivers within an hour. The causes are as much about the city as the sky.
Tropical thunderstorms can drop 50 millimetres or more in an hour. In the countryside much of that soaks into soil. In a growing city, roofs, roads and paved yards send almost all of it straight into drains that were often sized for a much smaller town. Where drains are blocked with plastic and silt, the water has nowhere to go but along the streets, and it collects in the lowest neighbourhoods first.
Lagos is low and coastal, and heavy rain there often coincides with high water in the lagoon, which slows drainage. Its wettest months run from April to July, with a second peak in September and October after a short August break. Accra’s worst flooding comes in the major rainy season from May to July; the flood and fire of 3 June 2015 remains a painful reminder. In Nairobi, flooding peaks during the long rains from March to May, as in 2024, when floods across Kenya killed hundreds of people, and informal settlements along the rivers suffer most.
Never walk or drive into moving water: 15 centimetres can knock an adult over and 60 centimetres can carry a car away, and open drains are invisible under brown water. If your home floods regularly, keep documents and electrics off the floor and know your route to higher ground. When the forecast shows heavy rain, especially an afternoon thunderstorm with a high rain chance, plan journeys for earlier in the day.