When deciding on onboard duds, divide your wardrobe between indoor and outdoor garments. The North Atlantic has unpredictable weather-patterns, so before you board ship, invest in some smart wool sweaters and a water-resistant jacket. Warm, weather-proof clothes will allow you to spend some time outside admiring the coastline. Depending on the month, women wearing dresses should stock up on stockings or tights.
Inside, cruise-liners are typically well-heated and cold-weather cruisers spend a lot of their time in dining rooms, ballrooms, cabins and game-rooms. Still pack that tux or evening gown for special dinners and dances.
New England air grows crisp in autumn and the sunlight thins. The moist atmosphere can make the air seem colder than it is.
For this reason, New Englanders themselves aren't known for "dressing up." Most residents of seaside towns wear drab workday clothes, like blue jeans, overalls and sweatshirts. Even in well-visited areas, like Cape Cod and Portland, the locals are a casual bunch; sports jackets and fancy dresses are veritable beacons of tourism. When they do show off their vestments, New Englanders are fond of peacoats and wool greatcoats.
But most importantly, stay warm and dry. Invest in some Gortex boots and rain-gear if you want to hike inland. Breathable and quick-drying fabrics are essential. In New England, practical fashions are the best fashions.
Back in the day, New England was famous for its galoshes and whalers' outfits. Later, upscale New Englanders like the Kennedy's set the local precedent, with their pleated slacks, Harvard sweaters and boat shoes.
These days, consider emulating the models in Lands' End or L.L. Bean catalogs. These clothiers are particularly popular in New England (L.L. Bean is based in Maine), and their wares are particularly suited to the region's rugged weather.