Based on 1,556 research-grade iNaturalist observations in Illinois, Groundhog is most often recorded in May; in Illinois it behaves like a summer visitor / breeder. It ranks #10 among mammals recorded in the state in our data.
Marmota monax
Groundhog in Illinois by month
Bars show research-grade observations per month. They mix true seasonality with how often people are outdoors, so treat small numbers with caution.
Also seen in Illinois in May
Eastern Cottontail
Eastern Gray Squirrel
White-tailed Deer
Eastern Chipmunk
Common Raccoon
Muskrat
Eastern Fox Squirrel
Virginia Opossum
Places to look in Illinois
State ParkCahokia
Botanical GardenMorton Arboretum
National ForestShawnee National Forest
Botanical GardenChicago Botanic Garden
Botanical GardenLadd Arboretum
State ParkStarved Rock State Park
FAQ
When does Groundhog appear in Illinois?
Mainly March–October, with the most records in May.
How common is Groundhog in Illinois?
It ranks #10 by number of iNaturalist observations among mammals in Illinois (1,556 records in our sample).