Union-Furnace, Ohio is a small rural community situated in the southeastern part of the state. The climate in Union-Furnace is considered humid continental, characterized by four distinct seasons. Summers are warm and humid, with average temperatures ranging from the high 70s to low 80s Fahrenheit, while winters are cold, with temperatures dropping into the 20s and occasional snowfall.

The hydrology in Union-Furnace primarily consists of small creeks and streams that flow through the area, eventually joining the Hocking River which is located to the west of the town. These waterways provide a habitat for various aquatic species and contribute to the region's natural beauty.

Outdoor enthusiasts in Union-Furnace can take advantage of several recreational opportunities. The nearby Wayne National Forest offers hiking trails, camping grounds, and hunting opportunities, allowing visitors to explore the scenic woodlands. The Hocking River provides opportunities for boating, fishing, and kayaking, while Lake Hope State Park offers a serene lake for swimming, canoeing, and paddleboarding. Additionally, the area boasts numerous parks and nature reserves, inviting residents and visitors to enjoy picnicking, birdwatching, and wildlife spotting.