Street trees in Seoul. (Yonhap)

Every summer, local district governments in Korea are tasked with tackling heat waves in resourceful ways.

But while mist-spraying and parasols can cool down the heat, street trees are more effective at keeping temperatures down, according to a new study.

Street trees create shade where temperatures are 15.4 degrees Celsius lower than their surrounding areas, according to a study published by the city-funded Seoul Institute of Technology earlier this month.

Outdoor shade canopies, a popular anti-heat measure adopted by local districts in Seoul, saw temperatures go down by 8.4 C.

Compared to canopies, street trees are 25 percent more effective at tackling heat, the study found. The “cooling fog” system, which sprays fine water particles, was estimated to bring down the temperature by 12 C.

The institute said the study was designed to find the best anti-heat measures to adopt, and research was conducted in parts of Seoul over four weeks between July and August.

The study, however, said the installment of canopies is “necessary” around pedestrian crossings where planting street trees is not allowed.

Growing grass, as opposed to artificial turf, also helped reduce heat levels.

When the temperature reached 32.5 C in Seoul Plaza, a full moon-shaped square outside the city hall, the area with natural grass was 23.6 C, a test by the institute found.

At parts of the plaza covered with artificial turf, temperatures of over 47 C were recorded.

During hot weather, asphalt surfaces were nearly twice as hot as green spaces and are thought to be a “major factor” behind the greenhouse effect in cities.

The findings will be used to introduce appropriate anti-heat measures for “heat wave hot spots” and high-activity areas across the city, the institute said.