According to a review of studies on park size and urban cooling effect, large urban parks with an area of more than 10 hectares (24.7 acres) provide the highest-intensity cooling effect as well cooling over the farthest distance from the park.
Aram, Farshid, Ester Higueras García, Ebrahim Solgi, and Soran Mansournia. “Urban green space cooling effect in cities.” Heliyon 5, Issue 4 (2019). https://doi.org/10.1016/j.heliyon.2019.e01339.