Ticks are thriving in Michigan because of a long-term expansion that keeps accelerating, driven by milder winters, wetter conditions, and a growing range of tick species pushing into counties where they were never seen before. What feels like a sudden explosion is actually a trend decades in the making, and 2025 is shaping up as another peak year.
Warmer Winters Let More Ticks Survive
Ticks don’t die off in winter the way mosquitoes do. Adult blacklegged ticks (also called deer ticks) burrow into leaf litter and essentially wait out the cold. The colder and longer the winter, the fewer survive to spring. But Michigan’s winters have been trending milder, and that shift is the single biggest factor behind rising tick numbers. More ticks survive to spring, they become active earlier, and they stay active later into fall. The Michigan Department of Health and Human Services has directly linked milder winters and longer, more humid summers to ticks being “active and out longer.”
Spring moisture matters too. Ticks dehydrate easily, so a wet spring creates ideal conditions for them to climb onto grass and low vegetation and wait for a host. Dry, hot summers suppress tick activity somewhat, but a warm and humid season keeps them questing for blood meals well into October.
Blacklegged Ticks Have Spread Across the State
Thirty years ago, blacklegged ticks were rare in Michigan. That’s no longer true. Their range has expanded steadily across both the Lower and Upper Peninsulas, and they’re now well established in large swaths of the state. Michigan State University Extension describes this as a 30-year expansion that shows no sign of slowing down. These ticks are relatively common in forested areas, and Michigan has no shortage of those.
The blacklegged tick is the species that transmits Lyme disease and anaplasmosis, two infections that have been climbing in Michigan alongside the tick population. Because this species was historically uncommon here, many residents aren’t used to checking for the tiny nymphal ticks (about the size of a poppy seed) that do most of the transmitting. That unfamiliarity can make a growing tick population feel even more alarming when people start finding them on their skin, their kids, or their dogs.
A New Species Is Moving In
Michigan isn’t just dealing with more of the same ticks. The Lone Star tick, a species historically found in the southeastern United States, has been pushing northward into the state. Researchers from Michigan State University documented this migration in detail. Between 2004 and 2016, only four individual Lone Star ticks were recovered from surveys across 35 counties. By 2020, that had changed: the species was found at seven sites across five southern Michigan counties, including Berrien, Branch, Cass, Ingham, and Huron. Berrien County now has what researchers consider an established population, confirmed across three consecutive years.
Lone Star ticks carry their own set of health concerns. The most unusual is alpha-gal syndrome, a condition where a tick bite triggers an allergic reaction to red meat. In areas where Lone Star ticks are common, alpha-gal syndrome is actually the leading diagnosed cause of severe allergic reactions. At least one Michigan resident with no travel history outside the state has already ended up in an emergency room with severe anaphylaxis linked to the condition. As this tick continues to establish itself in southern Michigan, alpha-gal cases will likely follow.
More Hosts, More Habitat, More Ticks
Ticks need blood meals at every stage of their life cycle: larvae feed on small mammals like mice, nymphs feed on anything from chipmunks to humans, and adults prefer larger hosts like white-tailed deer. Michigan’s deer population remains robust, providing a reliable host for adult ticks to feed and reproduce on. Suburban development that creates edges between woods and lawns is also ideal tick habitat, giving them access to both the shady, moist environment they need and the human and pet traffic they feed on.
Small mammal populations play an equally important role. White-footed mice are the primary reservoir for the bacteria that causes Lyme disease. When mouse populations are high (often following years with heavy acorn production), more larval ticks pick up the infection, and more nymphs emerge the following spring already carrying the pathogen. This creates a delayed effect where a good year for oak trees translates into a worse year for Lyme risk 12 to 18 months later.
When Risk Is Highest
Michigan’s tick season runs roughly from April through November, but the riskiest window depends on the species and life stage. Adult blacklegged ticks are active in spring and again in fall. The tiny nymphs, which are harder to spot and responsible for most Lyme disease transmission, are most active from late May through July. Dog ticks (the larger, more commonly encountered species) peak in late spring and early summer.
Because warmer temperatures are pushing the active season earlier and extending it later, the traditional advice to “watch out in summer” no longer covers the full window. Michiganders hiking or doing yard work on a warm day in March or November can encounter active ticks.
How to Protect Yourself
The most effective protection combines repellent with a post-outing tick check. The CDC recommends treating clothing and gear with 0.5% permethrin, which kills ticks on contact and lasts through several washes. For exposed skin, EPA-registered repellents containing DEET or picaridin provide reliable protection when used as directed.
Tick checks after time outdoors remain the simplest and most important habit. Blacklegged ticks generally need to be attached for 24 to 36 hours before they can transmit Lyme disease, so finding and removing them the same day dramatically reduces your risk. Pay close attention to hidden areas: behind the ears, along the hairline, in the armpits, behind the knees, and around the waistband. Showering within two hours of coming indoors helps wash off unattached ticks and gives you a chance to spot attached ones.
For your yard, keeping grass short, removing leaf litter, and creating a gravel or wood chip barrier between lawn and wooded areas reduces the number of ticks near your living space. Ticks avoid dry, sunny ground, so anything that eliminates shady, moist microhabitats at the edge of your property makes a difference.