Adults average 4-5 feet (122-152 cm) in length, although 6-7 foot (183-213 cm) specimens are not uncommon. Thermoreceptive pits are located between the labial scales. Females are larger than males. There are two color variations that are considered by some to represent two distinct subspecies. One is green to grayish-green and is found mainly in the eastern half of the range, while the other is yellow, orange and brown and occurs in some parts of the western side of the range. The green variant also tends to be about two thirds of the size of the yellow-brown variant.