These Illinois Lakes Are Crawling With Snakes (Here's Where To Watch Your Step)

Few things ruin an idyllic summer lake day like startling a snake on the trails or seeing the telltale shimmy of a long reptilian body cutting through the water. Thankfully, Illinois is home to only four venomous snakes — timber rattlesnakes, cottonmouths (also known as water moccasins), copperheads, and incredibly rare massasaugas. However, many of the state's 40 snake species hunt and seek shelter in the wetlands and resource-rich areas surrounding the most beautiful lakes in Illinois. These bodies of water serve as habitats for all manner of critters, from the endangered coachwhip to your run-of-the-mill garter snake and everything in between. However, for the snake-adverse, a few lake destinations in Illinois should be avoided at all costs or at least visited with caution.

Before going any further, keep in mind that none of the lakes on this list have a documented infestation problem at the time of writing. These are lakes that have notable snake populations, recorded through surveys, reports, and citizen science. In addition, snakes are vital to overall ecosystem health, and most don't want to come into contact with humans. "Typically, people's experiences with getting bitten are due to an interaction that was inadvertent," explained assistant professor Norman L. Beatty, M.D., FACP to University of Florida Health. "They stumble upon a snake or reach for something without seeing one camouflaged." If a snake crosses your path, give it ample opportunity to exit on its own and avoid reaching into places you can't see while out in nature — especially cool, dark spaces where snakes like to hide. 

Known for the crowd-attracting South Sandusky Beach, Rend Lake is a reservoir that covers over 18,900 acres near Sesser and Mt. Vernon. With over 19 miles of paved trails hugging the shores, waterfront camping, and some of the best crappie fishing in the state, it's no wonder Rend Lake is known as "Southern Illinois' Playground."

However, there's a chance you'll encounter a snake or two during your trip. Thanks to the expansive 162 miles of shorelines, northern water snakes (also known as the common water snake) and copperbelly water snakes make Rend Lake their hunting grounds. Both are non-venomous and play an important role in managing frog and small fish populations. Unfortunately, northern water snakes are often confused with cottonmouths and copperheads because of the dark bands across their bodies. Differentiating the two is difficult and requires a closer look than the casual lakegoer should undertake, so it's best to simply steer clear of all snakes at Rend Lake. 

It should come as no surprise that Rend Lake is a bit snakey, after all, it's only 45 minutes from Shawnee National Forest. Not only does the park host the whimsical "Gnome Roam" that's a one-of-a-kind storybook adventure, but it's also home to LaRue-Pine Hills-Otter Pond Research Natural Area. Known as Snake Road, this area is an epicenter of mass snake migration every spring and summer and a top destination for snake enthusiasts.

Smackdab in the middle of Central Illinois, Lake Shelbyville is an 11,100-acre manmade lake formed by damming the Kaskaskia River. It's a top destination for city dwellers seeking a couple of days on the water due to its location a little over an hour from Springfield, Illinois' bustling Route 66 stop packed with quirky attractions and historical sites. While relaxing on a rented pontoon boat or fishing in secluded coves, your chances of running into a snake are low. However, several species make their homes in the scenic uplands surrounding the lake, including the grasslands and wetland-lined shore. In addition, the Shelbyville State Fish and Wildlife Area's 6,000 acres welcome all sorts of animals, including raccoons and foxes which both eat snakes. 

If you're camping at one of the eight public campgrounds or hiking the 50 miles of trails, keep an eye out for massasaugas. Although these rattlesnakes are quite rare due to habitat loss, their Illinois territory technically expands into Moultrie County, which encompasses part of Lake Shelbyville. It's incredibly unlikely you'll encounter a massasauga here, but if you do, this venomous snake packs a serious punch, or rather bite. On top of this, spotting a northern water snake is a possibility, as it's one of the most common snakes seen near bodies of water in Illinois.

Situated about an hour from St. Louis, Missouri, in Clinton County, Carlyle Lake welcomes visitors with sandy beaches and a laid-back setting ideal for waterfront barbecues and sailing excursions. This reservoir spreads over 26,000 acres, providing plenty of opportunities to spot snakes in the water or slithering through the wooded shoreline. 

Snake identification communities on Facebook, like Illinois Snake Identification and Education, frequently feature posts highlighting snake sightings at Carlyle Lake. In early 2025, one boater reported 12 to 15 snakes swimming by his craft, although he was unable to provide an identification. Common snakes you might encounter include northern water snakes and non-venomous eastern garter snakes. It's impossible to estimate the exact number, but eastern garter snakes (also a member of the common garter snake family) can be found across the state, including along the banks of Carlyle Lake. 

While garter snakes are land dwellers, they are also known to swim, so you may encounter one during your day on the lake. However, they prefer to stay on land, where they hunt mice, frogs, worms, and even small birds. To learn more about local animals, including snakes, stop in at the Carlyle Lake Visitor Center and check out the Kids in Nature Discovery Center. 

Although not technically a lake, Cache River State Natural Area makes the list because it offers many of the activities visitors enjoy at lakes, including boating, canoeing, hiking, and fishing. Plus, many of the cypress swamp zones are lake-like, albeit rather still and shallow. Most importantly, it also shelters three of Illinois' venomous snakes —cottonmouths (water moccasins), copperheads, and timber rattlesnakes.

The other lakes on this list provide ideal habitats for Illinois' snakes, but at the Cache River, the snakes are considered well-known locals. "If you're not sure what I mean by 'beware,' then I guess I should spell it out," shared one reviewer on Tripadvisor. "(I'll spell it so little kids don't hear you say it... S-N-A-K-E-S.) Yep, there everywhere. Water moccasins. They love water, so they're right at home."

The cottonmouth bite is quite painful and requires medical attention. However, these snakes only occupy a small section of Illinois — the extreme southern tip of the state. As they prefer swamps and sloughs, they don't range any further north. If snakes make your skin crawl, you might want to also avoid these snake-filled lakes in Michigan and Texas' 68-species-strong snake population.