Merrill, Iowa is a small town located in Plymouth County, in the northwestern part of the state. The town experiences a typical Midwestern climate characterized by four distinct seasons. Summers are warm and humid, with average temperatures reaching the mid-80s°F (around 29°C), while winters are cold and snowy, with average temperatures hovering around 20°F (-6°C). Spring and fall bring pleasant temperatures in the 50s-60s°F (10-20°C).

Hydrologically, Merrill lies within the Big Sioux River watershed. The area is dotted with several small creeks and tributaries that eventually flow into the Big Sioux River. The river offers opportunities for fishing, boating, and other water-based activities. Anglers can find various species of fish, including bass, catfish, and walleye.

Outdoor enthusiasts in Merrill have access to numerous recreational opportunities. The surrounding area boasts several parks and nature reserves with hiking trails, campgrounds, and picnic spots. Nearby Plymouth County Conservation's Hillview Recreation Area offers opportunities for hiking, birdwatching, and hunting. Not far from Merrill, Stone State Park provides additional outdoor activities, such as camping, fishing, and wildlife viewing.