The incorporation of empirical data from 2021 to 2025 underscores climate change as a primary determinant of urban health in West Africa, with Nigeria bearing the greatest impact. The study found that increased disease severity was the major factor. The data in the review illustrate an unhealthy climate that drives up illness rates. The numbers presented indicate that the annual heat-wave exposure per person increased from 28 days in 2021 to 33.2 days in 2024, with a concurrent 8.6% increase in heat-related mortality. Lagos is the city that experiences the most rapid urban heat, with the earth’s surface temperature rising by 4.5°C from 2000 to 2022. Major flood events typically trigger outbreaks; the 2024 disaster displaced 1.3 million people and resulted in 7,485 cholera cases (Case Fatality Rate 4.3%), with a 63% increase in acute watery diarrhea. Social vulnerabilities largely shape health outcomes, so those effects hit harder in poor and informal areas with little or no infrastructure to mitigate risks. Among other risk factors in these locations, indoor temperatures can reach 35–40°C during heat waves, which is followed by a hospitalization spike of 15–25% at the time, and post-flood malaria cases can increase by 125%. The convergence of climate hazards with poverty, fragile health systems, and spontaneous urbanization exacerbates health crises in a compounded manner. Heat-health action plans, resilient urban planning enforcement, and the WASH infrastructure investment to safeguard the fast-growing urban population are among the core measures that need to be taken.