Climate & Cities
A heat plan is about finding people, not cooling buildings
Heat deaths concentrate among people who are isolated, immobile and indoors. The response is a contact list before it is a technology.
This is written to be used rather than admired. Each section below is a decision about heat emergency planning, and each one has a default.
Before you start
- Excess deaths in heatwaves occur predominantly indoors and among isolated older people.
- Night-time temperature is the critical variable for physiological recovery.
- Identifying at-risk residents in advance is the limiting factor in most plans.
The risk is social before it is thermal
Analyses of heat mortality repeatedly find the strongest risk factors are age, chronic illness, immobility and living alone. The common pattern is a person who cannot leave their home, has nobody checking on them and does not perceive the danger. Buildings matter through this lens: a top-floor flat with one aspect and no shading is dangerous for the person who cannot leave it.
A heat plan that addresses buildings without addressing contact is solving half the problem.
Nights are what kill
The body recovers from daytime heat during sleep, and that recovery requires the environment to cool. Sustained warm nights prevent it, and cumulative strain over consecutive days is what produces excess mortality. This is why the duration of a heat event matters as much as its peak, and why single-day forecasts understate risk.
On the ground, heat warning systems that trigger on multi-day forecasts rather than peak temperature reflect this better.
Cooling centres work only if people reach them
Air-conditioned public buildings offer relief and require the person to travel there in the heat of the day. The people at highest risk are the least able to make that journey, which is a structural weakness in the model. Transport to cooling centres, extended opening hours and locating them within walking distance all improve uptake.
At street level, outreach visits to identified residents address the group that cannot travel at all.
Identifying the vulnerable is the hard part
Registers of at-risk residents can be built from health records, social care lists, utility vulnerability schemes and community organisations. Data protection rules govern what can be shared and differ substantially between jurisdictions, so approaches are not transferable. Voluntary registration reaches only people who already engage with services, which misses much of the target group.
Neighbour and community networks fill part of the gap and are the least formal and most locally variable element of any plan.
Advice has to be specific and correct
General messaging about drinking water and staying inside is widely distributed and weakly acted upon. Practical instructions — close windows and shutters during the day, open them at night, use the coolest room, check on neighbours — are more actionable. Some standard advice interacts with medication and medical conditions, so anyone with a health condition should follow guidance from a qualified clinician.
Measured properly, messaging that reaches people who do not use the internet remains a persistent gap in most plans.
Local statute governs most of this, and it varies street by street.
The long-term answer is the built environment
Emergency plans manage the events that arrive; shading, ventilation, insulation, tree canopy and cooler public space reduce how severe they are. Retrofitting the housing occupied by the most vulnerable residents is the intervention with the largest long-run effect.
That housing is frequently the oldest, the least well maintained and the least likely to be prioritised. A city that runs an excellent heat plan every year and never changes its buildings is managing a problem it could be reducing.
The takeaway
The most important part of a heat plan is a list of names and someone to knock on the doors.
Cities are built by a thousand small permissions, not one big plan.
Questions readers ask
Why do heat deaths happen indoors?
Because the people most at risk are those who cannot leave home, and poorly performing buildings retain heat overnight. Indoor conditions can be worse than outdoor ones during and after a heat event.
Should windows be open or closed during a heatwave?
The general principle is to close windows and shading during the hottest part of the day and open them once outside air is cooler than inside. Local guidance and individual medical circumstances should take precedence.
