The southern flying squirrel is easily distinguished from other Nebraska tree squirrels by its smaller size and by its gliding membrane, or patagium, a fold of skin that extends from the wrist of the front leg to the ankle of the hind leg. When the front and hind legs are extended, the membrane forms a wing-like gliding surface. The furred, broad and horizontally flattened tail serves as a rudder and stabilizer during glides. The eyes are noticeably large, an adaptation for its nocturnal habits. The ears are more prominent than in other tree squirrels.
Whiskers are also prominent.
Southern flying squirrels are quite small. Adults usually are nine to 10 inches long including the tail, and they weigh between two and four ounces. Their fur is soft, silky and moderately long. The upper body is grayish to brownish in color, and the underparts are creamy white. The eyes are surrounded by a black ring, and a black border extends along the edge of the gliding membrane.