This paper investigates the fundamental performance of an evaporative cooling pavement system, which we propose, during summer. As part of this empirical study, two experimental mock-ups are developed. In one mock-up, water is pooled under paving blocks so that the water can be continuously absorbed and evaporated due to the block's capillarity mechanism. In another mock-up, no water is pooled underneath the paving blocks. The effects of the evaporation rate and water content of the paving blocks on the evaporative cooling performance were examined in these two systems through the long-term outdoors experiment. The results of this experiment showed that the surface temperature of the paving blocks depends on the evaporation rate and water content of the blocks in the no water supply system. In the water supply system, the evaporation rate was high and the block surface temperature remained approximately equal to ambient air temperature. These results indicate that the water supply system maintains a high cooling effect through the Japanese hot and humid summer.