Animal Crossing: New Horizons will sneak in its autumn update next week, on 30th September. Download it and you'll be able to get ready for Halloween (and also get a free Ring Fit Adventure item).
You'll be able to buy candy from Nook's Cranny and grow pumpkins to use as a crafting material for new spooky furniture items. You'll get blueprints for these from your fellow villagers.
There are new Halloween costumes to buy from the Able Sisters' shop, and some unhealthy-looking undead body paint and eye contacts to unlock with Nook Miles to make yourself look creepy.
On Halloween itself, from 5pm to midnight, the pumpkin-headed Jack will appear in your town. You'll be able to give your villagers candy in exchange for nice surprises. Or not, for a trick. New spooky emotes will be available.
Speaking of emotes, an update to the Nooklink app coming in October will let you emote in-game by using your smartphone. Handy!
Finally, there's word on the next Animal Crossing: New Horizons update, which will arrive in summer 2021 - joking - in late November. Expect Turkey Day and Toy Day (Thanksgiving and Christmas) preparations then.