Ticks in Illinois
Ticks are active in Illinois whenever the ground is not frozen, led by the Lyme-carrying deer tick. TickZone scores all 1294 Illinois towns every morning, so risk stays local: pick your town for today's number, a 7-day outlook, and what's driving it.
Tick season in Illinois
Tick season in Illinois runs whenever the ground is not frozen, roughly March through November, with two peaks. Nymph deer ticks, the poppy-seed-sized stage that causes most Lyme cases, peak from late May through July. Adult deer ticks make a second push in October and November, and on any winter day above about 40 F they can quest again. American dog ticks are busiest from April through July.
| Life stage | J | F | M | A | M | J | J | A | S | O | N | D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Deer tick nymphs | ||||||||||||
| Deer tick adults | ||||||||||||
| American dog tick | ||||||||||||
| Lone star tick |
Those are averages, and any single week can run hotter or colder than the calendar suggests. The daily score on every town page folds the season, the weather, and local habitat into one number each morning, so it is the safer way to time yard work, hikes, and pet prevention.
Highest-risk towns in Illinois (2026)
Illinois's highest-risk towns are spread across several counties, led by Marshall. The top 10 towns run 79 to 95 percent forest, ranked at peak season so the list stays stable.
- 1Hopewell Marshall CountyModerate at peak
- 2Rockwood Randolph CountyModerate at peak
- 3Tower Lakes Lake CountyModerate at peak
- 4Norwood Peoria CountyModerate at peak
- 5Trout Valley McHenry CountyModerate at peak
- 6Kenilworth Cook CountyModerate at peak
- 7Thebes Alexander CountyModerate at peak
- 8Elsah Jersey CountyModerate at peak
- 9Valley City Pike CountyModerate at peak
- 10Leland Grove Sangamon CountyModerate at peak
All Illinois towns, by county
Adams County · 14 towns
Alexander County · 5 towns
Bond County · 8 towns
Boone County · 5 towns
Brown County · 4 towns
Bureau County · 23 towns
Calhoun County · 5 towns
Carroll County · 7 towns
Cass County · 5 towns
Champaign County · 23 towns
Christian County · 13 towns
Clark County · 4 towns
Clay County · 6 towns
Clinton County · 14 towns
Coles County · 6 towns
Cook County · 119 towns · 2/100k Lyme
- Alsip
- Arlington Heights
- Barrington
- Barrington Hills
- Bedford Park
- Bellwood
- Berkeley
- Berwyn
- Blue Island
- Bridgeview
- Broadview
- Brookfield
- Burbank
- Burnham
- Calumet City
- Calumet Park
- Chicago
- Chicago Heights
- Chicago Ridge
- Cicero
- Country Club Hills
- Countryside
- Crestwood
- Des Plaines
- Dixmoor
- Dolton
- East Hazel Crest
- Elk Grove Village
- Elmwood Park
- Evanston
- Evergreen Park
- Flossmoor
- Ford Heights
- Forest Park
- Forest View
- Franklin Park
- Glencoe
- Glenview
- Glenwood
- Golf
- Hanover Park
- Harvey
- Harwood Heights
- Hazel Crest
- Hickory Hills
- Hillside
- Hodgkins
- Hoffman Estates
- Hometown
- Homewood
- Indian Head Park
- Inverness
- Justice
- Kenilworth
- La Grange
- La Grange Park
- Lansing
- Lemont
- Lincolnwood
- Lynwood
- Lyons
- Markham
- Matteson
- Maywood
- McCook
- Melrose Park
- Merrionette Park
- Midlothian
- Morton Grove
- Mount Prospect
- Niles
- Norridge
- North Riverside
- Northbrook
- Northfield
- Northlake
- Oak Forest
- Oak Lawn
- Oak Park
- Olympia Fields
- Orland Hills
- Orland Park
- Palatine
- Palos Heights
- Palos Hills
- Palos Park
- Park Forest
- Park Ridge
- Phoenix
- Posen
- Prospect Heights
- Richton Park
- River Forest
- River Grove
- Riverdale
- Riverside
- Robbins
- Rolling Meadows
- Rosemont
- Sauk Village
- Schaumburg
- Schiller Park
- Skokie
- South Barrington
- South Chicago Heights
- South Holland
- Stickney
- Stone Park
- Streamwood
- Summit
- Thornton
- Tinley Park
- Westchester
- Western Springs
- Wheeling
- Willow Springs
- Wilmette
- Winnetka
- Worth
Crawford County · 6 towns
Cumberland County · 4 towns
De Witt County · 7 towns
DeKalb County · 12 towns
Douglas County · 8 towns
DuPage County · 30 towns · 4/100k Lyme
Edgar County · 8 towns
Edwards County · 4 towns
Effingham County · 10 towns
Fayette County · 7 towns
Ford County · 9 towns
Franklin County · 14 towns
Fulton County · 20 towns · 18/100k Lyme
Gallatin County · 7 towns
Greene County · 9 towns
Grundy County · 12 towns
Hamilton County · 5 towns
Hancock County · 15 towns
Hardin County · 3 towns
Henderson County · 8 towns
Henry County · 14 towns
Iroquois County · 21 towns
Jackson County · 11 towns
Jasper County · 7 towns
Jefferson County · 9 towns
Jersey County · 6 towns
Jo Daviess County · 10 towns · 41/100k Lyme
Johnson County · 7 towns
Kane County · 23 towns · 4/100k Lyme
Kankakee County · 19 towns
Kendall County · 8 towns · 5/100k Lyme
Knox County · 14 towns
Lake County · 46 towns · 5/100k Lyme
- Antioch
- Bannockburn
- Beach Park
- Buffalo Grove
- Deer Park
- Deerfield
- Fox Lake
- Grayslake
- Green Oaks
- Gurnee
- Hainesville
- Hawthorn Woods
- Highland Park
- Highwood
- Indian Creek
- Kildeer
- Lake Barrington
- Lake Bluff
- Lake Forest
- Lake Villa
- Lake Zurich
- Lakemoor
- Libertyville
- Lincolnshire
- Lindenhurst
- Long Grove
- Mettawa
- Mundelein
- North Barrington
- North Chicago
- Old Mill Creek
- Park City
- Riverwoods
- Round Lake
- Round Lake Beach
- Round Lake Heights
- Round Lake Park
- Third Lake
- Tower Lakes
- Vernon Hills
- Volo
- Wadsworth
- Wauconda
- Waukegan
- Winthrop Harbor
- Zion
LaSalle County · 24 towns · 7/100k Lyme
Lawrence County · 5 towns
Lee County · 12 towns
Livingston County · 14 towns
Logan County · 10 towns
Macon County · 12 towns
Macoupin County · 27 towns
Madison County · 27 towns
Marion County · 13 towns
Marshall County · 8 towns
Mason County · 9 towns
Massac County · 3 towns
McDonough County · 10 towns
McHenry County · 27 towns · 7/100k Lyme
McLean County · 21 towns
Menard County · 5 towns
Mercer County · 10 towns
Monroe County · 6 towns
Montgomery County · 20 towns
Morgan County · 10 towns
Moultrie County · 6 towns
Ogle County · 13 towns
Peoria County · 15 towns · 8/100k Lyme
Perry County · 6 towns
Piatt County · 8 towns
Pike County · 17 towns
Pope County · 2 towns
Pulaski County · 7 towns
Putnam County · 6 towns
Randolph County · 14 towns
Richland County · 5 towns
Rock Island County · 15 towns
Saline County · 6 towns
Sangamon County · 25 towns
Schuyler County · 4 towns
Scott County · 7 towns
Shelby County · 11 towns
St. Clair County · 25 towns
Stark County · 4 towns
Stephenson County · 11 towns
Tazewell County · 16 towns · 5/100k Lyme
Union County · 6 towns
Vermilion County · 21 towns
Wabash County · 4 towns
Warren County · 5 towns
Washington County · 12 towns
Wayne County · 9 towns
White County · 10 towns
Whiteside County · 11 towns · 11/100k Lyme
Will County · 25 towns · 3/100k Lyme
Williamson County · 15 towns
Winnebago County · 11 towns · 5/100k Lyme
Woodford County · 15 towns
Illinois tick questions
- Are there ticks in Illinois?
- Yes. Illinois has ticks in every county, led by the deer tick (blacklegged tick) that spreads Lyme disease, along with the American dog tick and the lone star tick. They are active whenever the ground is not frozen, and today 584 of the state's 1294 towns are at moderate or high tick risk on TickZone's daily score.
- What types of ticks live in Illinois?
- Illinois has the deer tick (blacklegged tick), which carries Lyme disease; the American dog tick; and the lone star tick, which is reported in the state and causes alpha-gal syndrome. See the Illinois tick identification chart for photos and how to tell them apart.
- When does tick season start and end in Illinois?
- In Illinois, ticks are active whenever the ground is not frozen, roughly March through November. Nymph deer ticks peak in June and July and cause most Lyme cases, and adult ticks have a second peak in the fall. On any winter day above freezing, adult ticks can still bite.
- When is flea and tick season?
- Flea and tick season generally runs from early spring through late fall, peaking in the warm summer months. In Illinois, start prevention for pets and people in March and keep it up through November, since ticks can bite on any mild day.
- Which tick carries Lyme disease in Illinois?
- The deer tick, also called the blacklegged tick, is the tick that spreads Lyme disease in Illinois. The American dog tick and lone star tick do not carry Lyme.