New London, Ohio experiences a humid continental climate with four distinct seasons. Summers are warm and humid, with average temperatures ranging from the high 70s to low 80s°F. Winters are cold, with average temperatures in the mid-20s to low 30s°F. The area receives about 40 inches of precipitation annually, fairly evenly distributed throughout the year.

Hydrologically, New London is located near the Vermilion River and its tributaries, providing opportunities for fishing, canoeing, and kayaking. Outdoor enthusiasts can explore the lush natural landscapes at the nearby Firelands Rails to Trails, a popular biking and hiking trail. Additionally, New London Reservoir Park offers various recreational activities, including boating, swimming, and picnicking. With its climate and hydrological features, New London provides a range of outdoor opportunities for nature lovers and adventure seekers.