Impacts of extreme heat do not occur in isolation but often cascade across sectors; disruptions in energy infrastructure, for example, can quickly trigger failures elsewhere. New research shows that preventing extreme heat events from becoming disasters requires a systems-level approach that goes far beyond individual behaviour change.

Extreme heat is the deadliest climate hazard in Australia, causing more deaths than all other natural hazards combined. Yet it remains under-recognised as a disaster risk, and is often treated as an individual inconvenience rather than a collective challenge.

When we talk about dangerous heat, a huge part of the population switches off. ‘Toughing it out’ is a source of national pride.

Medical specialist and academic

New applied research using the Post-Event Review Capability (PERC) – a systematic methodology for examining disaster events to capture learnings for strengthening future resilience – reframes how we understand extreme heat. This first-ever PERC on extreme heat, delivered collaboratively by Australian Red Cross (ARC), Zurich Australia, ISET-International, Monash University, the International Federation of Red Cross and Red Crescent Societies (IFRC) and the Z Zurich Foundation, with support from the Zurich Insurance Group, examines extreme heat events in Adelaide, South Australia across the 2024-2025 summer. One of its central findings is clear: extreme heat becomes a disaster when it overwhelms the systems people depend on. Resilience therefore must be built at the systems level — not only at the level of individual behaviour.

How heat impacts cascade across systems

Extreme heat amplifies existing pressures across housing, health, infrastructure, and social services, with disruptions in one area often worsening impacts in another. When these systems are already stretched, extreme heat can push them beyond safe limits, turning a climate hazard into a systemic crisis.

Energy and other critical infrastructure: During extreme heat, increased use of air conditioning spikes demand for electricity, while transmission lines lose efficiency and transformers overheat. Power failures then disrupt cooling, water provision, transport, communications, and healthcare. Strengthening power system resilience and planning for continuity of critical services are foundational to reducing systemic heat risk.

Housing and urban development: When homes lack adequate insulation, it can rapidly lead to dangerous indoor conditions. Cooling systems lose efficiency, requiring more energy to achieve diminishing results. Dense development and hard surfaces further intensify the risks. Strengthening resilience requires heat-informed urban planning, climate-resilient building codes, and retrofitting existing housing to support passive cooling.

Urban greening and the natural environment: Healthy ecosystems help to moderate temperatures, but, extreme heat places sustained stress on these natural systems, reducing tree canopy, degrading habitats, and warming and deoxygenating water bodies. Increasing urban tree cover and integrating green and blue spaces into development can provide essential cooling services during extreme heat.

Health systems: Healthcare facilities often face the dual demands of unsafe indoor conditions combined with rising cases of heat-affected illnesses. It is vital to embed heat risk into healthcare planning, including strengthening data on heat-related illness and death.

Heat doesn’t affect everyone equally

During extreme heat, older people, outdoor workers, people with chronic illness and those without access to reliable cooling face disproportionate risk. When vulnerabilities are unrecognized or heat warnings do not reach the right people, impacts escalate rapidly. Identifying at-risk populations, planning inclusive responses (such as the Red Cross’ TeleRedi program), activating cool spaces and tailoring communication are critical entry points for reducing preventable harm.

Workplaces and schools are similarly affected. Extreme heat makes outdoor and poorly ventilated work unsafe, undermining livelihoods and productivity. Education is disrupted when heat affects sleep and concentration, when classrooms become unsafe, or when power and cooling systems fail. Integrating heat risk into workplace safety standards, adjusting schedules, and making schools heat-safe are essential for social and economic continuity.

There is no way I could work for two weeks straight in 35°C. It’s the cumulative effect — dehydration, lack of sleep — while still being expected to get the work done.

Parks and gardens supervisor

Despite these widespread impacts, heat is often not fully integrated into disaster management systems, partially due to the lack of clear triggers that define when it becomes dangerous. Without impact-based forecasting and tailored warnings, escalating risk can go unnoticed — particularly during compound events such as heat combined with bushfire or storms.

Finally, community awareness and cultural norms shape how all of these systems function. In Australia, where heat is often normalised as “business as usual,” the lack of early action or collective responsibility can result in higher mortality, economic disruption, interrupted education, and overloaded systems.

Extreme heat is not a single hazard with isolated impacts. It is a systemic risk that interacts with infrastructure, institutions, ecosystems, and social norms. This PERC demonstrates that reducing heat risk requires strengthening the systems that underpin everyday life. Explore the systems level impacts and entry points for extreme heat resilience via the Extreme Heat PERC reports – Heat stress at work, Understanding extreme heat and entry points for action, and Strengthening resilience to extreme heat: an Adelaide case study — which offer practical insights for practitioners and decision-makers working to build resilience in the face of extreme heat.

This is an edited version of an article that originally appeared on the Global Disaster Preparedness Center. You can view the original here.