Stewart Park on Cayuga Lake
Robert Treman State ParkFall in Ithaca is absolutely "gorges!" <-- I'm sure you noticed this on every shirt and mug in town. This is a reference to the many gorges in town. As a Californian, I thought summer was my favorite season until I saw the vibrant tree leaves in Ithaca in autumn. I would suggest venturing out to Watkins Glenn in mid October. It is an unforgettable sight! A drive or bus ride to NYC from Ithaca will also show you the true beauty of central NY. Various festivals and activities in town in the fall including: the Apple Festival, Ithaca Chili Cook-off with over 30 restaurants participating, Oktoberfest, Ithaca Film Festival, Restaurant Week, etc.
Cornell Campus in the fall
Winter prep: invest in snow tires if you have a car, a very warm winter coat and snow boots. I would suggest purchasing vitamin D as it is a problem here in the winter since the sun pretty much hides all winter. Winter is long but magical at times and filled with snow activities nearby.
When in doubt, visit this page. And this one.