Sorry, it has to do with the length of sunlight (including what shines through clouds). Otherwise, leaves in warm winter regions would never turn at all. It varies with latitude. That is why Canadian Thanksgiving (a harvest festival) is October 12 this year, and leaf-viewing has already started in northern states, while here, the only non-green leaves are due to drought, not temperature.
Lamberger
Sorry, it has to do with the length of sunlight (including what shines through clouds). Otherwise, leaves in warm winter regions would never turn at all. It varies with latitude. That is why Canadian Thanksgiving (a harvest festival) is October 12 this year, and leaf-viewing has already started in northern states, while here, the only non-green leaves are due to drought, not temperature.