Long Island beach connoisseurs know that early autumn is the best time to visit; the water stays warm into September and sometimes even early October, and the crowds thin considerably. Of course, if you love the action, you'll want to be here in summer, when everything's open and the weather is most predictable. Book rooms a couple of months in advance for summer travel. Spring usually bursts onto Long Island in late March; suddenly everything is newly green, the gardens awaken, the shorebirds build their nests, and even the ocean loses its winter gray and starts to sparkle. Winter is good for solitary, though cold and windy, beach walks, and it's the only time of year you'll see seals and sea turtles.