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Three-year Guildford study finds woodland can be 4.5°C cooler during extreme heat

University of Surrey researchers found all six green and blue spaces they monitored were cooler than a built-up site, with woodland showing the strongest protection during heatwaves.

By The TEA Editorial Desk · 28 August 2026

University of Surrey researchers installing temperature sensors in trees Image: University of SurreyOriginal source

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Three years of temperature monitoring around Guildford has produced a strong case for keeping cities green as summers get hotter.

University of Surrey compared woodland, grassland, lakeside, riverside, a pocket park and a green wall with a built-up location. During ordinary peak summer hours, every green or blue site was cooler, with woodland about 2.5°C lower than the built-up area.

Across ten extreme heat events, the woodland was 4.5°C cooler on during the daytime and sometimes more than 5°C to 6°C cooler. The built-up site recorded 54 heatwave days over the three summers, while the woodland recorded none.

The does not every tree instantly air-conditions the street beside it. It does provide long-term local that vegetation and water can materially change how much heat people experience in cities.