Adults average about 6–8 feet (2+ meters) in length, but may reach 10 feet (3 meters). Robustly built, it has a long head that is slightly distinct from the neck. The anterior supralabials have thermosensitive pits.
Scalation includes a pair of undivided parietal scales and a single loreal scale on either side of the head. On the body, the dorsal scales number 45-55 at midbody, the ventral scales 270-300, the anal scale is single, with 60-90 paired subcaudal scales.
The color pattern consists of a uniform, iridescent dark blackish brown dorsal color. The belly is a dull to bright yellow that includes the first few rows of dorsal scales. The throat is cream colored, while the upper labials are light gray-brown with dark brown or black spots.