Heat risk

We know that with climate change, London can expect to see hotter drier summers and warmer wetter winters. In the summer months, London is vulnerable to extreme heat episodes and heatwaves.

In July 2022 the Met Office issued the first ever Red warning, Level 4 heat alert, for exceptional heat. This heatwave was far more intense and widespread than previous heatwaves.

This meant impacts beyond the health and social care system, and even fit and healthy people were at risk. It caused:

• Fires at significant scale, destroying some London properties.
• The Fire Brigade had their single busiest day since World War 2.
• Temperatures reached 40.2° C at weather stations at St. James’s Park and Heathrow on 19 July 2022. 

Heat risk and the need to cool London is not just a summer problem. Overheating is a challenge all year round because many of London’s existing homes and buildings were not built for climate change – particularly hotter, drier summers and warmer wetter winters (the Met Office projects a greater chance of hotter, drier summers and warmer, wetter winters).

The result of extreme heat in summer, and the experience of occupants of existing homes and buildings that are not adapted for climate change, disproportionately impacts certain groups, especially those with pre-existing mental and physical health conditions, the very old and young, those on low incomes, outdoor workers, rough sleepers, and those with protected characteristics are at risk from and/or vulnerable to extreme heat. 

We are working with our stakeholders such as London’s boroughs, public health officials, academic institutions, community and voluntary groups and others to understand better how extreme heat and overheating impact Londoners and how we can reduce the risk of heat in the city, whilst protecting those most at risk and the vulnerable. We want to make living in, working in, and enjoying London a positive experience for all.

Through our planning policy, we are managing heat risk in new developments as well as increasing the amount of green space and vegetation to play a part in cooling the city.

Planning applicants are expected to mitigate the overheating risk as climate change leads to rising temperatures. The Energy Assessment Guidance explains how to comply with measures to reduce internal overheating risk in line with the London Plan’s cooling hierarchy. 

Following 2022 extreme summer temperatures and wildfires, the mayor pledged £3.1m for a new tree planting package to protect and future-proof London. Planting more trees in London will help cool the city and provide welcome shade. It will also help protect London from flooding. Tree planting is part of the Mayor’s mission to make London a greener, more liveable city, where everyone has access to healthy outdoor space.

Read on to find out more about some projects that have been tackling overheating in London, along with guidance and advice.