Karnack is located in the pine woods of Northeast Texas and beside Caddo Lake, one of the largest natural lakes in the Southeast. The surrounding country is mostly farm and timber land. According to The Handbook of Texas, Caddo Lake was one of the largest natural lakes in Texas before the construction of Caddo Dam in 1900 made the lake even larger. It is often called Texas' only natural lake, but many small natural lakes and oxbow lakes are found in Texas.
The climate in this area is characterized by hot, humid summers and generally mild to cool winters. According to the Köppen Climate Classification system, Karnack has a humid subtropical climate, abbreviated "Cfa" on climate maps.
Karnack is served by the Karnack Independent School District. Karnack Elementary School and Karnack Junior/Senior High School serve the community.
- Karnack, Texas from the Handbook of Texas Online
- Longhorn Army Ammunition Plant from the Handbook of Texas Online
- U.S. Geological Survey Geographic Names Information System: Karnack, Texas