Sumas, Washington is a small town located in Whatcom County, near the Canadian border. The climate in Sumas is classified as a temperate rainforest, with mild summers and cool, wet winters. The average annual rainfall is around 60 inches, making it one of the wettest areas in the state. The climate is influenced by the nearby Cascade Range, which blocks some of the rainfall, resulting in a rain shadow effect.

Hydrology constituents in Sumas are dominated by the Nooksack River, which flows through the town. The river serves as a vital water source for agriculture and supports various fish species, including salmon. Sumas Lake, which used to be a prominent feature in the area, was drained in the early 20th century for agricultural purposes.

Outdoor recreation opportunities in Sumas are abundant. The region offers access to the beautiful and rugged North Cascades National Park, where visitors can enjoy hiking, camping, and wildlife watching. The Nooksack River provides opportunities for fishing, kayaking, and rafting. There are also several parks and trails in and around Sumas, such as Sumas Mountain Regional Park, offering scenic views, biking, and horseback riding. With its stunning natural surroundings, Sumas provides ample opportunities for outdoor enthusiasts to explore and enjoy the area's unique climate and hydrology constituents.