Challenge
The July 2022 UK heat wave — which saw temperatures above 40 °C for the first time on record — exposed London’s acute vulnerability to extreme heat. Over 3,000 excess deaths were recorded nationally during the event. London’s densely built fabric, its thermal mass, and the legacy of homes designed to retain heat rather than shed it make heat waves uniquely dangerous for its 9 million residents.
London’s Heat Risk Response
The Mayor of London and the UK Health Security Agency have developed a multi-strand heat resilience strategy that combines public health intervention with long-term infrastructure change.
Cool Spaces Programme
Launched in 2022, the Cool Spaces scheme mapped and registered over 300 venues across all 33 London boroughs — including libraries, community centres, shopping centres and parks — as publicly accessible refuges during heat events. Interactive maps allow residents to find their nearest cool space by postcode.
Heat Health Alert System
The UK Health Security Agency’s Heat Health Alert service issues tiered warnings (from Level 1 preparedness through Level 4 emergency) to health and social care providers, enabling them to implement pre-agreed action plans. The service uses Copernicus C3S seasonal forecast data to extend the outlook horizon.
Green Roofs and Urban Greening
The London Plan requires major new developments to incorporate green roofs and walls. The London Green Roof Map — built on satellite thermal imagery — identifies buildings and areas where greening would deliver the greatest cooling benefit, guided by analysis from the EEA’s UHI tool.
Climate Justice Integration
The Climate Just tool was used to map heat vulnerability at borough and ward level, combining heat exposure data with social deprivation, age profiles and health indicators. This analysis directed Cool Spaces resources and outreach towards the most vulnerable communities.
Outcomes
- 300+ Cool Spaces providing refuge to vulnerable Londoners
- Heat Health Alert system integrated into NHS and social care protocols
- London Urban Heat Island monitoring published annually
- Target of 4 million square metres of green roofs by 2030
Lessons Learned
- Early warning systems only save lives if they trigger pre-planned actions — building these protocols takes years
- Mapping vulnerability explicitly prevents cool-space resources going to well-resourced areas
- Green roofs require planning policy mandates to achieve scale — voluntary uptake is insufficient
- Cross-agency co-ordination between health, environment and planning bodies is essential
Tools Used in This Case Study
Climate Tools Applied
