Irwin, Iowa is a small town located in Shelby County, in the western part of the state. The town experiences a humid continental climate, characterized by hot summers and cold winters. Average high temperatures in summer range from the upper 80s to low 90s Fahrenheit, while winter temperatures can drop below freezing, occasionally reaching single digits. Precipitation is fairly evenly distributed throughout the year, with an average of around 30 inches annually.

Hydrologically, Irwin is situated near the Boyer River, which flows through the southern part of the town. The river provides opportunities for fishing, canoeing, and other water-based activities. Additionally, there are several small lakes and ponds in the area that offer recreational fishing.

Outdoor enthusiasts in Irwin can explore a variety of recreational opportunities. The area is known for its scenic rural landscapes, making it ideal for hiking, biking, and bird-watching. The nearby Holly Springs State Forest provides a great destination for camping, picnicking, and nature photography. Additionally, there are multiple golf courses in the region for those interested in the sport. Overall, Irwin offers a tranquil setting for nature lovers and outdoor enthusiasts to enjoy the beauty of Iowa's countryside.