Description: This species commonly grows to more than 3.3 ft in length. The maximum recorded size is 4.97 ft. In Montana, specimens occasionally exceed 3.9 ft in length; the species reaches its maximum size in this region. One of the most characteristic features is the presence of three or more, usually four, inter-nasal scales.
Identification characteristics will vary depending on which subspecies is encountered. Generally, western rattlesnakes are usually lightly colored in hues of brown. Patches of dark brown are often distributed in a dorsal pattern. A color band may be seen at the back of the eye. The western rattlesnake group carries the distinctive triangle-shaped head and pit sensory organs on either side of the head. A key characteristic that can help differentiate a western rattlesnake from other rattlesnakes is the presence of two inter-nasals contacting the rostral.