As Mark Twain famously said about weather in New England, “There is only one thing certain about it: you are certain there is going to be plenty of it.”But at least some generalizations are possible.
For many, the best time of year is the fall, when the famed foliage is in its full splendor and days are crisp and cool, but not cold. If you plan on leaf-peeping, be sure to check ahead and find out where the foliage is most dramatic, as the color can vary enormously with time and latitude. In general, the leaves start changing in Maine  in late September, and work their way down to the Connecticut  coast by late October.
Summer is arguably the second-best time for a trip, especially if you’re spending time on the coast. Because of cold Atlantic currents, beaches don’t come into their own until late July and August. If you plan on traveling inland, however, be forewarned that August’s infamous humidity can make for a sticky time of it.
Winter brings the added appeal of skiing and other outdoor sports, and a fresh layer of snow can make rural areas quite romantic. The only time that New England lacks luster is in the spring, a brief season of mud and raw weather through which most locals grit their teeth. Or, as Twain put it: “Every year (New Englanders) kill a lot of poets for writing about ‘Beautiful Spring.’” Note that except around ski resorts, many hotels and museums also close during the low season of January–March (the last month of which is known as “mud season” in Vermont  and New Hampshire ).