A new heat map helps Vietnam prepare cities for a warmer future

Two possible El Niño scenarios projected for 2026 and 2027 have put Vietnam on alert for hotter temperatures, drought and water shortages. But the country's biggest heat challenge may not be how hot cities get, but where the heat hits hardest. What if city leaders knew exactly which streets and communities were most at risk?

That question sits at the heart of Urban Heat Resilience: Bridging Science, Policy, and Sustainable Design, a flagship study involving RMIT Vietnam Senior Lecturer and Research Fellow Coordinator Dr Tran Duc Trinh and regional partners. Supported by Australia's Department of Foreign Affairs and Trade (DFAT), the Stockholm Environment Institute, the Asia Disaster Preparedness Center (ADPC), and a consortium of organisations across Southeast Asia, the project explores how cities can better prepare for an increasingly hotter future.

Not every neighbourhood feels the same heat

For years, researchers have been able to identify urban heat hotspots from satellite imagery. But knowing where temperatures are highest is only part of the story.

Dr Trinh and his team wanted to understand something more important: who lives in those hotspots and how heat affects their daily lives.

By combining temperature data with social and economic information, the researchers mapped where extreme heat overlaps with vulnerable communities in Ho Chi Minh City and other cities in southern Vietnam. These include low-income households, older people, people with disabilities and residents of informal settlements, many of whom have fewer resources to cope with rising temperatures.

"The research is advancing further with the heat mapping tool and linking that with susceptible communities' data to understand the impact and offer data-driven mitigation solutions that fit local contexts," Dr Trinh said.

Dr Trinh’s team also examined the role of nature-based solutions such as parks, green spaces and green roofs. Their modelling found that increasing green and permeable surfaces in highly built-up areas could reduce heatwave days in hotspots by up to 24 days and shorten some heatwave events by more than 30 days. Rather than adding greenery wherever space is available, the research helps cities identify where these interventions can deliver the greatest cooling benefits.

A map for cooler, healthier cities

The implications extend well beyond research. Vietnam's cities are growing rapidly, and decisions made today about urban planning and infrastructure will shape how communities cope with rising temperatures in the decades ahead.

The report provides evidence that governments can use to identify priority locations, design heat prevention plans and integrate climate resilience into future development. Highly built-up areas with extensive concrete surfaces and limited vegetation can experience up to 100 heatwave days per season, according to simulations in the report. Without intervention, some areas could face an additional 40 to 60 heatwave days each year by mid-century. Identifying which communities are most vulnerable becomes more than a planning exercise. It is a critical step in protecting public health, strengthening climate resilience and ensuring that limited adaptation resources are directed where they can have the greatest impact.

"Our studies can quantitatively show the areas impacted severely by urban heat issues that call for mitigation actions," Dr Trinh said. "The findings and the tool developed in the project help inform targeted actions and future planning of urban heat resilience in Vietnam."

The research can also support urban designers, developers and environmental practitioners seeking to create cooler, healthier and more liveable cities. Instead of relying on assumptions, they can use evidence to guide investments in green infrastructure and climate adaptation measures.

Importantly, the work is already generating interest beyond Vietnam. During dissemination events, urban planning organisations and NGOs, including organisations from Indonesia, expressed interest in using the methodology to map urban heat hotspots, communicate with their urban housing projects on impact of extreme heat and guide mitigation planning. The growing interest reflects a shared challenge across Southeast Asia, where rapidly urbanising cities are grappling with rising temperatures and climate risks.

For Dr Trinh, this is only the beginning. Future research will explore how urban heat affects health, labour productivity and inequalities in access to cooling and green space across Vietnam and Southeast Asia. While evidence from countries such as Australia has linked extreme heat to higher hospitalisation rates and productivity losses, these impacts remain under-researched in many cities across the region.

"Urban heat mapping is a simple and intuitive way to support both communities and decision-makers to take their own actions," he said. "Working collectively through co-creation and multi-stakeholder collaboration will ensure a sustainable transition for urban areas facing climate risks."

As Vietnam braces for hotter conditions, the challenge is no longer simply understanding climate risks. It is acting on what we already know. Research like this is helping cities identify not just where temperatures are rising, but where intervention can make the greatest difference.

Behind every major shift is a story worth exploring. The Ripple Theory is a series of expert perspectives informed by research from RMIT University Vietnam. By connecting academic insight with real-world stories, the series helps readers gain a deeper understanding of the shifts unfolding across the economy, society, environment, and technological world, while exploring solutions and opportunities for what lies ahead.

Read Dr Trinh's full report here.

Story: Ha Hoang

Thumbnail: Duy’s House of Photo – pexels.com