The latitude correlation of cherry first flowering dates decreased at 48 Japanese stations in 1980–2025

At 48 Japanese stations, the correlation between latitude and cherry first flowering decreased from 1980 to 2025. The records did not show a clear decrease in the spread of dates across these stations. We used only the standard cherry species and kept the same stations in every year. Mean annual Pearson correlation fell from 0.936 in 1980–1999 to 0.905 in 2006–2025. Its linear trend was −0.0148 per decade (95% block interval −0.0233 to −0.0065). Spatial standard deviation changed from 11.06 to 10.65 days. Its trend was −0.385 days per decade, with an interval of −0.836 to +0.052. The fraction of station pairs with earlier northern flowering rose from 14.65% to 19.79%. The latitude result held before 2020 and after each station was omitted once. Full bloom dates did show a modest decrease in spread. These results show that latitude order and date spread give different information. They do not prove that spread stayed constant or that warming caused the change. The package contains raw source data, exact station panels, code, figures, and source records.

phenology · cherry flowering · Japan · latitude · spatial variation · fixed station panel · reproducibility