Cape Cod weather is really quite good, especially when you consider that the island stays about ten degrees warmer than mainland Massachusetts during the winter months. This is due to the warming effects of the Gulf Stream. In the summer, on the other hand, Cape Cod is generally about ten degrees cooler than the mainland, and this is primarily the result of consistent offshore winds. Fog and rain are rather common, though when you average it out, it's more often sunny on Cape Cod than rainy.
Cape Cod in Summer: Summer is hands down the best time to travel to Cape Cod, at least if you don't mind the summer crowds that are especially prevalent in July and August. This is when the Cape Cod beaches are at their very best, and any other number of fun pursuits can also be enjoyed when visitors aren't spending time with their feet in the sand. Daytime temperatures most often falling somewhere between 70 and 80 degrees Fahrenheit. Some days are humid, and fog can set in at times.
Cape Cod in Fall: Early fall on Cape Cod feels much like summer most years, though the signs of autumn start to set in relatively soon thereafter. In September and October, the leaves on the trees start to change color, and the summer crowds have gone. Swimming in the ocean can be enjoyed due to the still relatively warm water temps, and activities such as biking and hiking can be rewarding. Sweaters start to come in very handy in and around the start of October.
Cape Cod in Winter: While Cape Cod is most often warmer than the mainland in the winter, it can still get downright cold. The normal daytime temperatures during this cold season range between 30 and 40 degrees, though it can drop to minus zero on some occasions. Interestingly enough, people will tell you that it doesn't snow on Cape Cod, or at least it's not supposed to. Some winters see snow, however, and it's not unheard of for a blizzard to move in as late as early April. The best Cape Cod vacations that are taken in the winter arguably revolve around celebrating the holidays, as the island is quite festive at this time of year.
Cape Cod in Spring: For those who enjoy gardens and gardening, spring might just be the best time to visit Cape Cod. In late spring, the island in general is in full bloom. This is the rainiest time of year, so visitors are encouraged to pack some waterproof gear. Early spring on Cape Cod can be quite chilly, with daytime temps in the mid-40s common.