The Tick Guide
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When Are Ticks Active?

Most people think of ticks as a summer problem. They're actually a spring-through-fall problem in most of the country and a year-round problem in the South and on the West Coast. Knowing the timing helps you protect yourself when it matters most.

The biggest misconception I've had to unlearn is that cold weather kills them off. It doesn't. Ticks go dormant in leaf litter when it gets cold, but they revive whenever temperatures climb above 35 to 40 degrees Fahrenheit. In the Northeast, that can happen in January. I've found crawling ticks on myself in February after a mild stretch, something that caught me completely off guard the first time it happened.

The Window That Matters Most

Late May through July is the highest-risk period in most of the northern US. That's when deer tick nymphs are active, and nymphs are responsible for the majority of Lyme disease infections in humans. They're poppy-seed small, they move slowly, and they're painless. People don't feel them attach. They go undiscovered for the full 24 to 48 hours needed for disease transmission in a way that larger adult ticks rarely do.

This is not a reason to panic about every tick check. It's a reason to be systematic about it during those specific weeks, especially with kids.

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Month by Month (Northeast and Midwest)

January
Low / dormant
Adult deer ticks can still be active on mild days above 35-40 degrees. If you've had a warm week and you've been outside, still check. Most ticks are dormant under snow or leaf litter.
February
Low / dormant
Same as January. Watch for warm spells. Adult deer ticks that didn't find a host in fall are still looking. In mild winters, activity can pick up earlier than expected.
March
Moderate
Adult deer ticks become active as temperatures rise. American dog ticks start appearing in the warmer parts of the month. The ground is thawing, leaf litter is wet, and tick questing begins in earnest.
April
Moderate to high
Adult deer tick activity peaks in early spring. Dog ticks active. Lone star ticks starting to emerge in southern and mid-Atlantic areas. Start checking after every outdoor outing.
May
High
Nymph deer ticks become active mid-month. This is the start of the highest-risk window. By Memorial Day weekend, nymph activity is significant across the Northeast and Midwest. All tick species increasingly active.
June
Peak
Nymph activity at its highest. Dog tick adults peak. Lone star ticks active and aggressive across the South and Mid-Atlantic. If you are going to get a tick-borne disease, June is when the odds are highest. Check every day.
July
High
Nymph activity begins tapering off late in the month but still significant through mid-July. Lone star adults still active. Larvae beginning to hatch and feed on rodents. Hot and dry weather reduces surface tick activity somewhat.
August
Moderate
Nymph season winding down. Larvae active on small mammals but rarely encountered by people. Lone star ticks still present in the South. Hot dry months tend to push ticks deeper into shaded vegetation.
September
Moderate
Adult deer ticks emerging in northern areas by late September. Lone star ticks still active. The fall window opens and people sometimes forget to check because summer is over.
October
Moderate to high
Adult deer tick activity picks back up significantly. These are the ticks that fed as nymphs last spring and molted into adults over summer. They're larger and easier to see, but they're active. Hiking and hunting season without tick checks is a real exposure.
November
Moderate
Adult deer ticks remain active until temperatures drop consistently below freezing. In warmer years, this can mean activity well into November. Leaf raking and late-season yard work keep this a relevant month.
December
Low
Activity drops with cold. However, adult deer ticks can still be active on warm days. The first consistent cold snap usually pushes most surface activity to a halt.
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How It Differs by Region

Southeast and Gulf Coast

Ticks are active essentially year-round. Mild winters mean lone star ticks and dog ticks never fully stop. Deer tick populations exist but the lone star tick is the dominant concern. Year-round tick checks and prevention are the only sensible approach.

Mid-Atlantic and Southern New England

One of the heaviest tick-burden regions in the country. Long tick seasons, high deer populations, and established Lyme disease risk. Peak window roughly April through November with a real fall resurgence of adult deer ticks. Nymph season in May and June is especially serious here.

Midwest

Season runs April through October generally. Deer tick populations are established and expanding westward. Lone star tick range expanding northward from the south. American dog tick common across the region. The Upper Midwest follows similar patterns to the Northeast but the season starts a few weeks later.

Rocky Mountain states

Rocky Mountain wood tick active from March through early July at lower elevations, often through August at higher elevations. This is the primary season for Rocky Mountain spotted fever in that region. Deer tick populations are limited in the interior West but present in some areas.

Pacific Coast

The western black-legged tick is active in a different pattern than its eastern cousin. In California, nymphs peak in spring and early summer. Adults are most active in fall and winter. Lyme disease exists here but at lower rates than the Northeast. California's tick season is genuinely year-round in many coastal areas.

Tick season is expanding. Multiple long-term studies have documented that ticks are becoming active earlier in spring and staying active later in fall as average temperatures rise. The maps and calendars from 10 or 15 years ago understate current risk in many regions. If you're in the Northeast and you're not checking for ticks in October, you're missing a real window.
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