Martha's Vineyard weather is pretty mild in general. For starters, this island off the Massachusetts coast tends to have warmer winter temps than mainland destinations like Boston, and the summers are cooler on average. Add in the oft-comfortable spring and fall conditions, and it becomes evident that there really isn't a bad time to visit.
Summer: The best time to travel to Martha's Vineyard is arguably the summer season. This is when the beaches are at their prime, and it's also when the restaurants, shops, and other attractions are operating at their peak levels. Fresh seafood is available in good supply during the summer, as is sunshine, and stunning sunsets cap it all off. It can get hot in Martha's Vineyard during the summer season, though the temperature rarely top 90 degrees Fahrenheit. In July, the average high is around 80 degrees, while the average low is around 68 degrees.
Fall: Unless you have your heart set on a beach vacation, the fall can be a great time to visit Martha's Vineyard. The temperate climate of the island usually translates to moderate fall days, though it can get quite brisk. In early fall, daytime temps can get as high as 90 and dip as low as 42. As October rolls around, daytime temps are in the mid-50s. New England is known for its beautiful fall foliage, so you might keep this in mind when planning a Martha's Vineyard visit. Also, the summer crowds are gone, as are the summer rates at the Martha's Vineyard hotels.
Winter: In the winter, Martha's Vineyard is cold, though while it might be snowing on the mainland, it can be raining on the island. The fact that it is surrounded by the Atlantic Ocean explains why Martha's Vineyard often has warmer winter temperatures than the rest of Massachusetts. The ocean breezes help warm the air. Daytime temperatures are usually in the 30s during the winter months, and it often dips into the 20s or lower at night and when extra-icy cold fronts move in.
Spring: Spring is another best time to visit Martha's Vineyard. Sure, this is the rainiest season on average, and it can be quite cool at times. That being said, a spring day in Martha's Vineyard can also be warm and sunny, and there's just something about being there when all the vegetation starts to come to life. You can enjoy a wide range of outdoor activities during the spring, and lack of crowds is hard to find fault with. Early spring can see maximum highs averaging around 50 degrees. In later spring, the daytime temps are often in the 70s, and it's not uncommon for them to jump up into the 80s.