• Every spot starts from its typical peak date, from years of foliage reports.
• Temperature: this autumn is compared with the same weeks of the last 3 years. Each 1 °C warmer delays color about 2.5 days; cooler brings it forward.
• Frost: a hard frost (−2 °C or colder) since September speeds things up about 3 days.
• Drought: under half the normal rain since August brings color about 3 days earlier and makes it duller.
• Brilliance rewards sunny days of 10–22 °C with cold nights, which build the reds, and penalizes warm nights and drought.
• Best days combine expected color with the weather. Strong wind strips leaves, which lowers color for the days after.

Modeled from weather data (Open-Meteo: ERA5 history plus forecast models), not live observation. Local elevation and aspect change timing by a week or more.