Does a hot summer trigger an early autumn?
Fruits and berries that we normally associate with autumn can ripen early during a hot summer. But there are other autumnal changes that are unaffected or even slowed by a long, hot summer. Leaves won’t lose their green colour until the nights start to get chilly, because cold temperatures are needed to break down the chlorophyll pigment. Also, birds decide when to migrate south for the winter by the shortening day length, not the weather.