As a born and raised Long Islander, of course I'm going to slightly biased and say Long Island is the best place to be any time of year, but there's something extra special about the island during autumn. And here's why:
1. Moderate Fall Weather
Sure there are days when it's 40 degrees and pouring rain (thank Joaquin for those), but for the most part, Long Island experiences the epitome of fall weather-crisp dry days followed by chilly nights. This is perfect weather for all the fall activities Long Island has to offer.
2. So. Many. Festivals
There's literally some sort of fall or Halloween festival/parade/etc every weekend during the entire month of October. Some of the highlights include a ginormous spectacle of jack-o-lanterns in Westbury Gardens, and the Long Island Fair in Old Bethpage.
3. U-Pick
Drive out east, to Riverhead and Calverton, and you're slammed with farm after farm where you can pick your own apples and pumpkins all season long. My personal favorite is Lewin's Farms in Calverton, which is a Long Island fan favorite (for good reasons). After visiting one of the renowned U-Pick farms, you'll probably be eating apple cobbler for a month straight, so start preparing yourself now.
3. Bremiere Farm
This little farm stand in Riverhead has without a doubt the best pie you will ever eat in your entire life. They offer nearly 20 different flavors, and not to mention a huge selection of jams and other baked goods like cookies. They also sell fruit, let's be real here, I only go for the pumpkin pie.
4. Roasted Corn
Sticking to the theme of going out east, make sure you stop by a farm stand and grab yourself roasted corn, or as I like to call it, the 8th Wonder of the World. Personal recommendation is Lewin's farm stand (of course) which also offers their own homemade seasoning. 
5. Haunted Houses
Though I am probably the farthest thing from a fan of haunted houses, Long Island has dozens of haunted houses, trails, and even a whole forest. From what I've been told (because I will never set foot there — ever), Bayville Scream Park is the next closest thing to being chases by an actual chainsaw-yielding delusional clown. As a pre-teen I ventured to Schmitt's Haunted Mansion, and started crying when someone jumped out at me in broad daylight. So if being scared sh*tless is what floats your boat, then you're in luck on Long Island.
6. Ghost Tours
As you probably guessed, ghost tours are not exactly my cup of tea either. But if you're an avid Ghost Hunters watcher, then I recommend finding yourself a nice ghost tour in Old Bethpage and experiencing the real thing. There's also a host of haunted locations on the island that you aren't technically allowed to explore, but what are teenage years if not for trespassing and urban exploring old psychiatric hospitals (I'm looking at you KPPC). 
7. It's absolutely beautiful.
Maybe it's the bias coming through again, but Long Island during fall is incredibly beautiful during the fall. There's a plethora of foliage that makes for some pretty high quality pictures I'm sure you're going to post on Instagram. Lucky for you though, because there are so many amazing parks to visit, ranging from small, local parks, like Blydenburgh, to Bethpage State Park. 
