In order to clarify the long-term phenological shift caused by the urban heat island phenomenon, this study investigated the relationships between flowering dates of Cerasus × yedoensis ‘Somei-yoshino’ and the air temperatures in 24 cities in Japan. It was confirmed that the flowering date was accelerated as the temperature rises during the flower-bud growing period. The actual number of flowering acceleration days tended to be smaller than the expected ones. This is thought to reflect the delay in dormancy breaking due to the rise in temperature during the dormancy breaking period, and this tendency was particularly observed in cold sites. This result shows that there is a difference between sites in the flowering acceleration for the same temperature rise, it should be considered when comparing phenological shifts between some cities. In the group of sites where the average temperature during the flower-bud growing period and the average lowest temperature during the dormancy breaking period were medium, the temperature rise tended to be small. Within each group with similar air temperature condition, the features of “large decrease in NDVI” or “small NDVI in 1985” were commonly seen at sites where the temperature rise were large. However, these features did not explain the relationship between land cover change and temperature rise at all points.
