Sullivan, Ohio is a small village located in Ashland County, in the northern part of the state. The climate in Sullivan is characterized by warm summers and cold winters, typical of the Midwest region. Summers are generally mild with temperatures ranging from the mid-70s to mid-80s Fahrenheit, while winters are colder with temperatures often dropping below freezing.

The hydrology of Sullivan is primarily influenced by the Black Fork Mohican River, which flows through the village. The river provides opportunities for various water-based activities such as fishing, kayaking, and canoeing. Additionally, there are several nearby lakes and reservoirs that offer additional recreational opportunities.

Outdoor enthusiasts in Sullivan can explore the surrounding natural areas, including Mohican State Park. This park is known for its scenic hiking trails, campgrounds, and opportunities for bird watching. The area also offers opportunities for hunting, horseback riding, and biking.

Overall, Sullivan, Ohio offers a pleasant climate with distinct seasons, a vibrant hydrology system, and a variety of outdoor recreation opportunities for nature lovers and adventure seekers.