Autumn — late September through October — is the peak time. The Connecticut River Valley turns spectacular colours and the town is at its most photogenic. The combination of period architecture, wide tree-lined streets, and New England foliage is about as good as this part of the world gets.
Spring and summer are quieter and equally pleasant. Many historic house tours run from May through October; check ahead in winter as some properties close and hours are reduced. Historic Deerfield's houses are at their most welcoming in the cooler months when the light inside is softer and the guides have more time for questions.