The escalating urban heat island (UHI) effect in urban areas has intensified the need for effective cooling strategies. Porous asphalt pavement emerges as a promising solution due to its ability to retain percolating rainwater, leveraging evaporative cooling to mitigate the UHI effect. Predicting the cooling impact of permeable pavement prior to installation is essential for comprehending its influence on the thermal environment. In this study, embedded thermocouple temperature monitoring within the pavement was proposed as a new method to predict and monitor the presence of water for evaporation. The experiment, simulating a 24-h cycle with periods of light and darkness, confirmed that water loss is exclusive to surface evaporation. Results indicate that water-retaining pavements can significantly reduce surface temperatures by up to 40 °C, suggesting their viability in mitigating UHI effects in urban roads. Furthermore, a three-day simulation demonstrated the sustained effectiveness of the water's cooling effect. The study establishes a clear correlation between the evaporation rates measured by weight and temperature changes recorded by thermocouples, while also noting that temperature change rates alone may not be a reliable indicator of water presence due to other influencing environmental factors.