February warmth was linked to longer first-to-full cherry bloom intervals in 69 Japanese station records, 1953–2025

We tested the time from first cherry flowering to full bloom in Japan. We used 3,530 paired on-site records at 69 weather stations in 1953–2025. The model controls station means, station linear trends, spring temperature, and baseline winter climate. A warm December–February mean was linked to a longer interval. We then split winter into two periods in an exploratory test. At the median station winter climate, a 1°C higher February mean was linked to a 0.66-day longer interval. The 95% crossed block bootstrap interval was 0.49 to 0.83 days. The December–January slope was −0.04 days per °C, with an interval of −0.24 to +0.15. The February link remained positive in both record halves and all sample checks. Its size fell when first flowering date and later temperature were added. These controls also changed the early-winter slope. The interval trend was +0.08 days per decade, with a 95% cluster interval of −0.08 to +0.24. Thus the annual weather link does not establish a long-term increase. The data do not identify a chilling mechanism. The package preserves raw JMA files, hashes, code, all checks, and reproduction steps.

plant phenology · cherry · Japan · temperature · winter · bloom interval · open data