IN temperate countries, heat is a summer exception. In South-East Asia, it is a permanent, intensifying condition. There is no heat season here, there is only heat, compounded year on year, degree by degree.
We grew up with it. We assume we are adapted to it. We are not. What has changed is not that it is hot. What has changed is that it is now lethally hot, for longer, and for more people at once.
When the mercury climbs, the human body enters a physiological emergency. The heart pumps harder, diverting blood towards the skin to cool itself.
For the young and healthy, this is manageable. For the elderly, the outdoor worker, or those with diabetes or cardiovascular disease, this is where the system fails, sometimes fatally, in an unventilated room or by a roadside in Kedah.
Research published in The Lancet Planetary Health journal found that each 1°C rise in mean temperature is associated with a 2% to 5% increase in excess mortality in tropical and subtropical regions – higher than the global average because populations here are already operating near physiological limits. A 2023 analysis of 700 cities across 43 countries found heat-attributable deaths accounting for nearly 1% of all mortality, with South-East Asian cities disproportionately represented at the high end.
Beyond death counts, we are also seeing a rise in chronic kidney disease from heat-induced dehydration among plantation and agricultural workers, and emerging evidence linking sustained heat exposure to accelerated cognitive decline, a silent multiplier of Malaysia’s growing dementia burden.
This risk is not evenly distributed. The World Health Organisation estimates heat exposure among older people increased 54% globally between 2000 and 2019; a trend accelerating fastest in Asia.
Adults over 65 face up to four times the risk of heat-related death compared with younger adults, due to reduced thermoregulatory capacity, polypharmacy, and social isolation. Malaysia’s elderly population is set to double by 2040. We are inheriting a serious demographic vulnerability, and we are not yet treating it seriously.
Singapore has stopped treating heat as background noise. It has elevated heat to a matter of national security, economic strategy, and population health, and invested accordingly. Its Centre for Climate Research projects daily mean temperatures exceeding 35°C by 2100, incompatible with outdoor work and lethal for unsupported elderly populations.
Singapore recognised early that air-conditioning is not a solution – it is a carbon-emitting, grid-straining symptom that deepens the underlying problem. Instead, the island state’s Urban Redevelopment Authority now mandates cool corridors, green roofs, and urban heat island mitigation as non-negotiable planning requirements.
The country’s Manpower Ministry has issued binding wet bulb globe temperature (WBGT) thresholds that legally trigger mandatory work-rest cycles for outdoor workers – enforced, not advisory. (WBGT tells us the risk of heatstroke more accurately by measuring humidity and radiant heat in addition to air temperature.)
And Singapore has committed over SG$100mil (RM312.3mil) in climate adaptation research and development, with a significant share directed at urban heat. This is what treating heat as a first-order national risk looks like.
Malaysia does not need another standalone heat action plan. What we need is to embed heat governance into every policy instrument already in motion, and to do it now, while the legislative and regulatory windows are open.
The National Planetary Health Action Plan (NPHAP) already encodes the principle that human health and planetary stability are inseparable. But principle without operational architecture is poetry, not policy. The NPHAP must carry specific, funded, enforceable heat commitments, not as an annex but as a central pillar.
Malaysia’s forthcoming Climate Change Act offers a rare legislative window: Heat must be written into it not as a general climate risk, but as a named, health- specific hazard with accountability structures attached. This is not the moment to draft a new document. It is the moment to use the ones we have.
Concretely, this means four things:
> Early interventions: Health-based early warnings that trigger specific public health interventions such as cooling centre activation and outdoor work pauses before physiological thresholds are crossed, disaggregated for outdoor workers, the elderly, and schoolchildren.
> Urban cooling mandates: These must be written into the Climate Change Act: cool roofs, permeable surfaces, urban forest corridors. Incentives have not moved the needle. Mandates will.
> Enforceable occupational standards: WBGT-triggered work-rest cycles and hydration protocols written into the Employment Act, not left to employer goodwill, for delivery riders, construction workers, and plantation labourers.
> Ageing population protection: Heat vulnerability mapping overlaid with demographic data to identify and fund outreach, subsidised cooling, and primary care protocols, particularly for residents of PPR public housing without cross-ventilation.
The cost of heat-related illness, lost labour productivity, and premature death already exceeds any investment in prevention. Singapore understood this calculation early.
The heat is already here. The frameworks are in place. What is missing is not plans. What is missing is the will to integrate them. Malaysia’s leadership in the region will not be measured by targets set for 2050. It will be measured by whether we protect our most vulnerable people from the heat that is already here in 2026.
Prof Tan Sri Dr Jemilah Mahmood, a physician and experienced crisis leader, is the executive director of the Sunway Centre for Planetary Health at Sunway University. She is the founder of Mercy Malaysia and has served in leadership roles internationally with the United Nations and Red Cross for the last decade. She writes on Planetary Health Matters once a month in Ecowatch. The views expressed here are entirely the writer's own.
