Sapporo

• Japan Meteorological Corporation forecasts Sapporo's maple to colour on Nov 4 (round 2, released Oct 1).
• Its past forecasts typically missed by 4.3 days.
• In Sapporo, peak usually lasts 4 days, from colouring to leaf-fall (median, JMA records).
• Method: the JMC forecast blended 50/50 with the last ~10 years of JMA records, both updated as days pass without colouring.
• Future days are capped at 85%: weeks ahead, nothing is certain.
• JMA has not yet recorded colouring of Sapporo's specimen maple.
• In a normal year (1991–2020) the maple colours around Oct 28.

Ginkgo

• Japan Meteorological Corporation forecasts Sapporo's ginkgo to colour on Nov 3 (round 2, released Oct 1).
• Its past forecasts typically missed by 4.9 days.
• In Sapporo, peak usually lasts 7 days, from colouring to leaf-fall (median, JMA records).
• Method: the JMC forecast blended 50/50 with the last ~9 years of JMA records, both updated as days pass without colouring.
• Future days are capped at 85%: weeks ahead, nothing is certain.
• JMA has not yet recorded colouring of Sapporo's specimen ginkgo.
• In a normal year (1991–2020) the ginkgo colours around Nov 4.