Africa’s Informal Settlements Face a Growing Heat and Health Crisis

Extreme heat is becoming a test of whether African urban systems can protect people whose homes trap heat, whose work keeps them outdoors, and whose access to water, healthcare and cooling is already constrained. In rapidly growing informal settlements, the same temperature can produce very different health outcomes depending on income, housing quality and public services.

A new systematic review, "Health Impacts of Extreme Heat Events in Disadvantaged Urban Communities Across Africa: A Systematic Review," published in the journal Climate, brings that inequality into sharp focus. The study synthesizes evidence on how extreme heat affects residents of disadvantaged urban communities across Africa. It finds clear evidence of heat-related illness, worrying signals on mortality, and a deeper structural problem: heat risk is being amplified by poverty, poor housing, weak infrastructure and political exclusion.

Following PRISMA guidelines, the researchers searched 11 academic databases and considered peer-reviewed studies published from 2010 to 2024 in English, French or Portuguese. Of 96,608 records screened after duplicate removal, only 21 studies met the final inclusion criteria. Seventeen examined morbidity and four mortality, with evidence heavily concentrated in South Africa, Kenya and Tanzania.

Heat Is Becoming an Inequality Multiplier

The review shows that extreme heat is already associated with a wide range of health problems in disadvantaged urban settings. Across the included studies, residents reported dehydration, heat exhaustion, heatstroke, headaches, skin rashes, cramps, dizziness, sleep disruption and severe thermal discomfort. Some studies also linked high temperatures with worsening cardiovascular and respiratory conditions, while others identified impacts on mental health and pre-existing illnesses.

The burden can be substantial. In one Accra study, 46% of respondents reported dehydration and heatstroke, while research in Dar es Salaam found thermal discomfort affecting more than 70% of participants. The review also found evidence that heat can aggravate conditions such as hypertension, respiratory illness, pneumonia, diarrhoeal disease and other existing health problems, turning extreme temperatures into a multiplier of already fragile health.

Mortality findings are more limited and less uniform, but they are still important. Research from Nairobi found that temperatures above locally defined heat thresholds were associated with child mortality and deaths from non-communicable diseases, while another Nairobi study did not find a statistically significant relationship between heat and years of life lost. South African evidence also showed that, under the conditions studied, cold-related excess mortality exceeded heat-related mortality.

The variation argues against one-size-fits-all heat policy. African cities differ sharply in climate, housing, population health, infrastructure and adaptive capacity, so a threshold that signals danger in one location may not work in another. The policy challenge is therefore not simply to issue heat alerts, but to build local systems that connect meteorological risk with health surveillance and community vulnerability.

Poor Housing and Weak Services Turn Hot Days Into Health Emergencies

According to the review, temperature alone does not determine who gets sick. Nineteen of the 21 studies examined vulnerability factors, repeatedly pointing to the interaction of low income, informal employment, overcrowding, poor-quality housing, insecure water access, weak sanitation, limited healthcare and land insecurity. Heat becomes most dangerous when these disadvantages reinforce one another.

Housing is a particularly powerful amplifier. Poorly insulated structures made from corrugated metal and other heat-absorbing materials can become dangerously hot during the day and remain hot at night, depriving residents of recovery time. Evidence from disadvantaged settlements found extremely high indoor temperatures, while overcrowding and inadequate ventilation further intensified exposure.

Water access adds another layer of risk. During extreme heat, households need more water for drinking, washing and cooling, yet poorer communities may rely on shared, intermittent or costly supplies. Limited access to safe water raises the risk of dehydration precisely when demand is highest, making urban water security an essential component of heat adaptation rather than a separate infrastructure issue.

Informal workers face a particularly harsh double exposure. Street vendors, construction workers, delivery workers and others may spend long hours in direct heat because they cannot afford to stop working, then return to homes that offer little thermal protection. For households without social protection, paid leave or reliable healthcare, avoiding heat exposure may simply not be an economically viable option.

The Evidence Is Alarming and Geographically Thin

The review is valuable partly because it exposes how little is still known. More than 80% of the included evidence came from South Africa, Kenya and Tanzania, with only isolated studies involving Cameroon, Egypt, Nigeria and Ghana. Despite a multilingual search strategy, no eligible French- or Portuguese-language studies were included in the final synthesis, leaving large parts of francophone and lusophone Africa effectively absent from the evidence base.

The gap has direct policy consequences. Cities cannot design credible heat-health strategies if they lack local evidence on temperature thresholds, vulnerable groups, disease patterns and effective interventions. The absence of data does not mean the absence of risk; it may instead reflect weak surveillance, limited research funding and underdeveloped health-information systems in precisely the places where vulnerability may be greatest.

The review itself also warrants caution. Eight studies were rated definitely low risk of bias and five probably low risk, while six were assessed as probably high risk and two as definitely high risk. Mortality studies generally showed stronger internal validity than morbidity studies, reflecting important differences in study design and data quality.

Most included studies used cross-sectional or mixed-methods designs, while rural disadvantaged communities and grey literature were excluded. The diversity of methods and outcomes also prevented the researchers from conducting a meta-analysis. The result is not a precise continent-wide estimate of heat-attributable illness or death, but a strong warning that the burden is real, socially patterned and still inadequately measured.

Africa Needs Heat Adaptation That Starts With Cities, Not Thermometers

Heat adaptation must move beyond forecasts and emergency messaging, the study warns. Governments need heat-health strategies that connect public health with housing standards, urban planning, water supply, sanitation, occupational protection and social policy. Short-term measures can include targeted warnings, hydration access, outreach to high-risk households and protections for outdoor workers, but deeper gains will depend on reducing structural exposure.

For development agencies and international institutions, the findings strengthen the case for investing in urban heat surveillance, resilient housing, neighbourhood-level cooling, primary healthcare and local data systems. Businesses, particularly those relying on outdoor or manual labour, should increasingly treat extreme heat as a workforce health, productivity and continuity risk rather than merely an environmental issue.

The findings also connect directly, by reasonable policy inference, with SDG 3 on health, SDG 6 on water and sanitation, SDG 10 on inequality, SDG 11 on sustainable cities and SDG 13 on climate action. The wider development lesson is that climate resilience cannot be separated from basic service provision: where housing is unsafe, water unreliable and healthcare inaccessible, adaptation will remain shallow regardless of how sophisticated the forecast.

Future research needs to become more geographically representative, longitudinal and policy-oriented. The authors call for deeper investigation of urban governance, informal land tenure, inequalities in public investment and macroeconomic constraints, alongside research that separates immediate low-cost interventions from medium-term reforms and longer-term structural change.