Frogs in Illinois: Identification Guide and Best Places to Start

Where are frogs most commonly found in Illinois?

Frogs in Illinois are most often seen in and around water: marshes, ponds, swamps, slow-moving streams, and even roadside ditches after rain. In the northern part of the state, look for them in wooded wetlands and along lake edges. Southern Illinois, with its cypress swamps and bottomlands, hosts a wider variety. Backyards with a small pond or rain garden can also attract them, especially during breeding season.

What season and weather conditions are best for spotting frogs?

The best time to spot frogs in Illinois is from late March through June, when temperatures warm and breeding activity peaks. Warm, damp evenings after a rain are ideal – that's when frogs move to breeding sites and call loudly. Early spring can yield chorus frogs and spring peepers, while summer brings bullfrogs and green frogs. During dry spells, frogs stick close to permanent water, making ponds your best bet.

How can you quickly identify common Illinois frogs?

Start with size, color, and call. The American bullfrog is large (up to 8 inches), green or brown, with a deep 'jug-o-rum' call. Green frogs are smaller, with a banjo-like twang. Gray treefrogs have bumpy skin and a short trill; they change color from gray to green. Leopard frogs are spotted and often found in grassy fields near water. Listen to calls online or use a frog ID app to match what you hear.

See our state animal guide for the next step.

What are the best tips for spotting frogs in your backyard?

You don't need a wetland to see frogs. A simple garden pond or even a birdbath at ground level can attract them. Leave leaf litter and log piles for hiding spots. Shine a flashlight at night over the pond – you'll often see eye shine or frogs sitting at the water's edge. Turn off outdoor lights to reduce disturbance. Check out our Illinois wildlife page for more backyard tips.

How do you tell frogs apart from toads in Illinois?

Frogs have smooth, moist skin and long legs built for jumping. Toads have warty, dry skin and shorter legs, moving in hops rather than leaps. Toads also have prominent parotoid glands behind their eyes. In Illinois, common toads include the American toad and Fowler's toad, which are often found in gardens. For a full species list, visit our frog hub.