The Pennsylvania Department of Conservation and Natural Resources (DCNR) claims: “Pennsylvania has a longer and more varied fall foliage season than any other state in the nation -- or anywhere in the world.”
Mother nature typically paints Southwestern Pennsylvania in spectacular colors for the first 3 weeks of October, with some nice colors already visible in late September among the still predominantly green foliage. Here are the best places to see spectacular fall foliage: https://backpackandsnorkel.com/USA/Pittsburgh/Foliage/