<p>Among heat island mitigation measures, the mitigation effect of green spaces within cities has been the subject of many studies, and its effectiveness has been demonstrated from multiple perspectives. Kyoto, a western city in Japan, suffers from extreme summer heat caused by the heat island effect and its inland topography. Therefore, it is necessary to clarify an effective greenspace layout for heat island mitigation in inland areas to address the heat in Kyoto. This study examined the heat island mitigation functions of hypothetical greening scenarios in Kyoto City using the Weather Research and Forecasting model. The results indicated a relationship between the green space layout and day/night temperature. If the increase in green cover ratio was the same between the scenarios, the lower the greening density and the larger the area, the greater the temperature decrease during the nighttime and the smaller the decrease during the daytime. The results also suggest that the average temperature of a city can increase depending on the location of green spaces. In the scenario of greening the central street of Kyoto City, the average temperature in the urbanised area increased by 0.007&#xa0;°C during the daytime. This is hypothetically thought to be due to an increase in humidity in the air caused by greening, which decreased the temperature-lapse rate. These results suggest that greening upwind and upslope areas may be effective in mitigating the daytime heat island effect over a wide area.</p>