Add together all the UK’s household gardens and they cover an area three times larger than all the country’s nature reserves combined. But as the demand for car parking increases, many front gardens are being paved over, with research showing that this loss of green is adding to the urban heat island effect, particularly at night.

In 2005, about 7.5% of the UK’s front gardens were paved; by 2025 that had risen to 55%, according to Royal Horticultural Society estimates. Those hard surfaces absorb heat during the day and then slowly release the heat overnight. By contrast, leafy green gardens release moisture into the atmosphere, which helps to cool the air as the water evaporates.

A Chinese study published in Nature Scientific Reports last year showed that changing paved gardens back to grass could reduce night-time temperatures by as much as 0.5C, and adding trees would double the benefit, bringing 1C of night-time cooling. And some heat reduction can be achieved without losing your parking space: even small additions such as a planting strip, a hedge or a tree can make a difference. London’s “De-pave your garden” programme provides tips on how to go from grey to green and help to keep your neighbourhood cooler when the next heatwave rolls in.