This ecoregion has a humid continental climate with warm summers and cold winters.
This ecoregion is bordered by the oak-dominated Northeastern coastal forests on the coastal plain to the south, the Gulf of St. Lawrence lowland forests on the coasts and islands of the Gulf of Saint Lawrence, and to the north and northeast the Eastern forest-boreal transition and the Eastern Canadian forests. There is also a disjunct patch of forest-boreal transition on the Adirondack Mountains.
In Canada the New England-Acadian forests ecoregion includes the Eastern Townships and Beauce regions of southern Quebec, half of New Brunswick and most of Nova Scotia, and in the United States northwestern Connecticut, northwestern Massachusetts, Lake Champlain and the Champlain Valley of Vermont, and the uplands and coastal plain of New Hampshire, and almost all of Maine. This entire area is sometimes referred to as the Atlantic Northeast. Specific areas include the Bay of Fundy coast, northern Appalachian Mountains including the uplands and the Saint John River valley of New Brunswick and the highlands of the Nova Scotia peninsula with the highest peaks being the White Mountains of New Hampshire.
The climate consists of warm summers and cold snowy winters with the Atlantic Ocean bringing rain all year round. The seaboard lowlands of this region, which extends to mid-coastal Maine, exhibits a more mild climate and has a somewhat distinct vegetation in which hardwoods play a more important role.
The forests of this area were radically cleared for agricultural land by the 19th century and then renewed as many of these farms were abandoned following the migration westward. Today the area is largely a mosaic of habitats influenced locally by micro-climatic differences (especially proximity to the Atlantic, and ecological disturbances). Essentially, there are four important community types which show considerable diversity and blending across this physiographic province. These communities are: alpine communities on the highest mountains, coniferous forests, northern hardwood forests, and wetlands. There are no clear boundaries between the coniferous forests and the hardwood forests in the New England-Acadian ecoregion. The prevalence in the canopy of red pine (Pinus resinosa) and red spruce (Picea rubens) distinguish the transition forests of New England from those in the Great Lakes region to the west.