Peak fall foliage in New England usually runs from late September through late October. Color moves south and downhill as the season goes on: northern Vermont, New Hampshire, and the mountains of northern Maine peak first, in late September into early October, while coastal Connecticut and Rhode Island peak last, in late October.
Peak color in any one spot usually lasts about one to two weeks before the leaves start to drop, and southern coastal areas typically peak two to three weeks after northern Vermont. Exact timing shifts from year to year with temperature, rainfall, and elevation.
Source: Visit New England, “Fall Foliage in New England”.
Image: Fall foliage at Missisquoi National Wildlife Refuge, Vermont, U.S. Fish and Wildlife Service (public domain), via Wikimedia Commons.