Since New York State is a four-season destination, the best time to visit depends on what you want to do.
Summer is peak season, accounting for about 40% of New York State tourism. From June to August, the weather is pleasant and mostly sunny, though it tends to be humid. Temperatures usually remain below 85°F (29°C), except in the vicinity of New York City and Long Island, which is about 10°F (6°C) warmer than the rest of the state year-round. Summer weather is ideal for travel; the problem is that everyone else thinks so, too. Parklands and campgrounds are filled with vacationers, especially on weekends. Cities throng with sightseers, making for long lines, sold-out events, and high prices.
Fall, from September to November, is another extremely popular time to visit. Upstate, the air turns to crisp jacket weather in September, but farther south summertime lingers until early October. New York's beautiful fall foliage is a huge draw, especially in mid-October -- the best time to catch trees sporting brilliant reds and golds. Expect country inns, B&Bs, and state and national parks to be particularly busy over Columbus Day weekend.
Contrary to popular belief, winter temperatures aren't miserable -- they normally range from about 15°F (-9°C) to as high as 40°F (4°C) in New York City. The snow, on the other hand, can be brutal. Infamous "lake-effect" snowstorms can dump several feet at once on Buffalo and surrounding towns, prompting Thruway and airport closings. Most of upstate New York is blanketed in snow from December to March. Although statistically winter is the slowest time for tourism in New York, it is high season for the state's ski destinations, and parks are still active with winter-sports lovers. New York City, which welcomes a steady flow of visitors all year long, is extra-jammed during the holidays thanks to Christmas festivities at Rockefeller Center, holiday shopping, and New Year's Eve in Times Square.
The spring thaw begins in March, but it's not unusual for snow to fall in April, or even May. There are spring showers, but the average amount of precipitation is no heavier than in summer or fall. Rainfall remains fairly constant from May to November at approximately 3 to 4 inches per month. If you enjoy the quietly melting snow and fresh spring breezes, this season may be your golden opportunity to indulge in outdoor activities before the summer rush.