What are The 3 Most Venomous Snakes Slithering Through Pennsylvania?

While most of the slithering creatures you encounter—like the common Garter Snake or the dramatic Black Rat Snake—are harmless, three species pack a potent, venomous punch.

Copperhead SnakeThough fatal snakebites in Pennsylvania are statistically rare (the last confirmed fatality was a camper in Elk County in 2015), the danger is real. Encounters are on the rise as suburban development pushes further into snake territory. Whether you are trekking the Appalachian Trail or just walking the dog in a wooded park, here is the definitive guide to the three venomous snakes you need to respect in the Keystone State.

1. The Northern Copperhead (Agkistrodon contortrix)

• Danger Level: Moderate (The most common venomous bite in PA)
• Where they hide: Statewide. Found in rocky ridges, wooded hillsides, and frequently in suburban backyards in Southern and Central PA.

If you see a venomous snake in Pennsylvania, odds are high it is a Copperhead. They are the most widely distributed venomous snake in the state. Unlike rattlesnakes, they have no warning system. Instead, they rely on incredible camouflage to blend into dead oak leaves.

• ID Tip: Look for the "Hershey’s Kiss" pattern. Dark brown, hourglass-shaped bands on a tan or coppery body. From the side, the dark bands look like the famous chocolate candy.

  
  
  

2. The Timber Rattlesnake (Crotalus horridus)

• Danger Level: Very High
• Where they hide: Mountainous Regions. Central and Northern PA (The Poconos, PA Wilds, Laurel Highlands).

The Timber Rattlesnake is an icon of the Pennsylvania wilderness. While they are generally docile and will rattle to warn you away, their venom is significant. In Pennsylvania, this snake comes in two distinct color "phases":

1. The Yellow Phase: A yellow or tan body with dark brown crossbands.
2. The Black Phase: A dark, almost charcoal-black body where the pattern is hard to see.

• ID Tip: A large, heavy body, a broad triangular head, and a distinct rattle at the end of a black tail.

  
  
  

3. The Eastern Massasauga (Sistrurus catenatus)

• Danger Level: High (but encounters are statistically near-zero)
• Where they hide: Extremely localized. Found only in a few western counties (Butler, Venango, Mercer) in wetlands and prairie habitats.

Often called the "Swamp Rattler," the Massasauga is Pennsylvania’s smallest and rarest venomous snake. It is an Endangered Species in the state. Sightings are incredibly rare and are usually celebrated by biologists rather than feared by hikers. In late 2025, confirmed sightings in Western PA excited conservationists but served as a reminder that these "ghosts of the swamp" are still out there.

• ID Tip: Small (rarely over 2 feet), with a row of dark, saddle-shaped blotches down the back and a tiny rattle that sounds like a buzzing insect.

The Myth: The Water Moccasin

Let’s be clear: There are no Cottonmouths (Water Moccasins) in Pennsylvania.

Every year, anglers on the Susquehanna or Delaware River swear they saw one. They didn't. The range of the Cottonmouth ends hundreds of miles south in Virginia.

• What you are seeing: It is almost certainly a Northern Water Snake. These non-venomous snakes are aggressive, will bite if grabbed, and flatten their heads to look dangerous, but they are not vipers.

Safety & Legal Warning

In Pennsylvania, the Timber Rattlesnake is a regulated game species (requiring a permit to hunt), and the Massasauga is totally protected. Indiscriminate killing of snakes is illegal.

What to do if bitten:

1. Call 911 immediately.
2. Stay Calm. A racing heart pumps venom faster.
3. Remove Constriction. Take off rings, watches, and tight boots immediately.
4. Do NOT use a tourniquet, cut the wound, or apply ice.

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Respect the wild. Keep your eyes on the trail, your dog on a leash, and give every snake the right of way.

Video: Timber Rattlesnake vs. Copperhead Identification in PA A guide by the PA Fish & Boat Commission on identifying the state's venomous reptiles.