How urban trees turn down the heat

4 August 2023 3 minute read

Trees can cool the air by up to 8 degrees

We’ve just witnessed the world’s hottest July on record, after reaching record-breaking temperatures in June in the UK. As unprecedented and unbearable heatwaves become the “new abnormal” worldwide, soaring temperatures are exacerbated in cities due to the urban heat island effect.

Trees work wonders by reducing temperatures on hot days. Heat maps released last month show that across 5 major English cities, areas with more trees and green spaces are up to 5 degrees cooler. The Food and Agriculture Organisation of the United Nations state that strategically planted urban trees can cool the air up to 8 degrees.

Recognising this direct impact, Trees for Cities are on a mission to plant, protect, and promote more urban trees in local communities—support us today to help reduce the escalating effects of the climate crisis.

What's an Urban Heat Island?

Cities are classified as urban heat islands due to their relative warmth compared to rural areas, fuelled by human activities such as transport emissions and concrete surfaces that absorb heat.


of global CO2 emissions are accounted for by cities according to the United Nations Framework Convention on Climate Change

The vast majority of us live in towns and cities: 80% and rising in the UK. With more of us moving to metropolitan areas, increased temperatures are only set to intensify. The urban heat island effect also contributes to poorer air quality, as well as a rise in heat-related illnesses. So, what can help us manage our safety in cities? Trees are an important part of the solution.

Trees are a welcome shady refuge on hot days

The cooling effect of trees

Our Projects Director Suzanne Simmons recently discussed the cooling effect of trees in cities on the Reasons to be Cheerful podcast:

One of the most tangible benefits of trees is around reducing urban heat by between 5 and 8 degrees. It doesn't sound like a lot on its own—but this makes a huge difference to thermal comfort and can also reduce the heat pressure on buildings—the impact of very intense heat.

Suzanne recalls the welcome shady refuge that trees brought when we surpassed 40 degrees in summer in the UK last year. Trees for Cities told Sky News that we need to shift our focus and funding towards greening urban areas, where the urban heat island effect comes into play:

Protecting trees for future generations

At Trees for Cities, we know that it’s just as critical to care for urban trees as it is to plant them. It can take between 25 and 50 years for a tree to reach the right level of maturity to unlock all of its benefits, so watering and tending to growing trees will get them on the right track to give back. During heatwaves, it's especially vital to water urban trees to make up for this short supply. Did you know you can play your part too?

50 litres

of water is the recommended amount of weekly water to give a tree for its first three years during the summer

You can help plant and protect more trees

To date, Trees for Cities have planted over 1.7 million trees, with the help of our incredible supporters. Despite this astonishing effort, The Climate Change Committee say the UK as a whole needs to be doubling its rate of hectare coverage to meet our net zero targets, in response to a recent report by the Forestry Commission.

Help us plant urban trees for all, by all, and have local impact on a national and global scale. Your support is invaluable in connecting communities to nature!

Donate to Trees for Cities and together we can help cities grow into greener, cleaner and healthier places for people to live and work worldwide.