What is Heat Stress — and Why Does It Matter?


As global temperatures rise, heat stress is fast becoming one of the most urgent urban challenges in North-West Europe. The Cool Neighbourhoods project places this issue at the heart of its work — because for many vulnerable communities, extreme heat isn’t just uncomfortable, it’s life-threatening.

But what exactly is heat stress? Who is most affected? And how can cities respond?



What is Heat Stress?

Heat stress happens when the human body is unable to cool itself down effectively during high temperatures. This can lead to symptoms ranging from exhaustion and dehydration to life-threatening conditions like heat stroke, especially among:

  • Elderly people
  • Babies and young children
  • People with chronic illnesses
  • Residents in poorly ventilated or poorly insulated homes
  • Outdoor workers and those in high-density housing

Heat stress is worsened by the Urban Heat Island (UHI) effect, where cities become significantly hotter than surrounding rural areas due to concrete, asphalt, traffic, and lack of greenery.

Why is this a problem in our neighbourhoods?

In many older, historic, or socially deprived areas:

  • Green space is limited or poorly maintained
  • Buildings lack insulation or shade
  • Paved surfaces retain and radiate heat
  • Vulnerable groups are less likely to have access to cool indoor environments

These conditions make such neighbourhoods particularly vulnerable to heatwaves, which are growing more frequent, intense, and longer-lasting due to climate change.

What are the impacts?

Unchecked heat stress can lead to:

  • Increased hospital admissions and premature deaths
  • Lower productivity and learning outcomes (e.g. in schools or workplaces)
  • Physical discomfort and sleep disruption
  • Higher energy costs (e.g. for air conditioning or fans)
  • Reduced biodiversity and ecological health

How is Cool Neighbourhoods addressing this?

The project tackles heat stress through a combination of:

Neighbourhood Heat Stress Action Plans (NHSAPs)
Tailored roadmaps for local authorities to identify and reduce heat risks.

The Liveability Index
A data-driven tool that highlights heat-vulnerable areas and tracks resilience.

Greening and Cooling Interventions
New parks, trees, water features, and shading in pilot areas to physically cool the environment.

Citizen Science & Mapping
Community-led temperature tracking and identification of hotspots to guide action.

Training & Awareness
Workshops, campaigns, and learning materials to empower residents and planners.

Who benefits?

Everyone — but especially:

  • Vulnerable residents whose health is at risk
  • City planners and engineers who need practical tools for climate adaptation
  • Schools, housing providers, and care services managing indoor environments
  • Local authorities responsible for urban sustainability

What’s next?

As the project scales up, tested solutions from pilot sites will be shared across Europe — helping neighbourhoods everywhere become cooler, healthier, and more climate-resilient.

Stay tuned as the Cool Neighbourhoods partnership launches new publications, dashboards, and open-source tools in late 2025!

 


What is the Cool Neighbourhoods Liveability Index?