Tick season in New Hampshire is nine months long — not three. Blacklegged ticks become active above 40°F, which means late March is already tick territory. This guide covers the month-by-month risk timeline, why May and June are the most dangerous months for Lyme transmission, which species are active when, and exactly when to schedule yard treatment in Seacoast NH.
The critical thing most homeowners don't know: tick season in New Hampshire starts in late March, not May. Blacklegged ticks (deer ticks) are active any time temperatures rise above 40°F — and Seacoast NH winters regularly produce days above that threshold.
NH DHHS tick surveillance tracks confirmed tick encounters and Lyme cases across Rockingham and Strafford counties year-round. The pattern below reflects that data combined with blacklegged tick lifecycle research from the University of Rhode Island TickEncounter Resource Center.
The October secondary peak catches more NH residents than almost any other tick pattern. After a summer of diligence, families drop their guard in fall. Adult blacklegged ticks are fully active through October — and fall ticks carry the same Lyme infection rate (36%) as spring ticks. Treat September–October like a second spring.
Nymph ticks — not adult ticks — are responsible for the majority of Lyme disease cases in New Hampshire. Understanding why means understanding the May–June risk window.
Adult blacklegged ticks are roughly sesame-seed sized (~3mm) and visible with careful inspection. Nymphs are poppy-seed sized (1–2mm) — many people handle them without realizing what they are, or never find them at all during a body check. A nymph embedded in a skin fold or covered by hair is almost impossible to spot without deliberate, careful searching.
Nymph season peaks in May and June — exactly when families are getting back outside after winter. Gardening, yard work, hiking, kids playing in the backyard: all of these activities happen at maximum intensity during peak nymph season. The tick calendar and the human calendar line up badly in the Seacoast NH spring.
In New Hampshire, the Lyme infection rate among nymph blacklegged ticks is similar to adults — approximately 20–36% depending on the surveyed population and location. Seacoast NH (Rockingham and Strafford counties) consistently shows infection rates toward the higher end of that range. One in three nymphs in the Seacoast is infected.
Studies estimate that a majority of people who develop Lyme disease never recall finding a tick. This is almost entirely a nymph phenomenon — nymphs are small enough that bite sites are painless and easily missed during checks. By the time symptoms appear (3–30 days for a bullseye rash), the tick is long gone and the patient has no memory of exposure.
A mid-April yard treatment puts a tick barrier in place before nymph season peaks. Waiting until Memorial Day to schedule treatment means you've already missed 2–3 weeks of the highest-risk window. In Seacoast NH, where tick density in suburban wooded-edge yards is among the highest in the state, early treatment is not optional — it's the entire strategy.
Three species are relevant to Seacoast NH homeowners. Each has a distinct seasonal pattern, disease risk profile, and activity window. Knowing which tick you found tells you how urgently to act.
Active: March–November, with adult peaks in April–May and October–November. Nymphs peak May–June.
Size: Adults ~3mm (sesame seed). Nymphs 1–2mm (poppy seed). Larvae barely visible (~0.5mm).
Diseases: Lyme disease, Anaplasmosis, Babesiosis, Powassan virus.
NH Lyme rate: ~20–36% of adults infected; nymph rate similar in Seacoast NH.
Active: April–July, peaking in May–June. Largely dormant in August heat.
Size: Adults 5–6mm unfed (watermelon seed). Engorged females reach 12–15mm — visually alarming but easier to find.
Diseases: Rocky Mountain Spotted Fever (rare in NH), Tularemia. Does NOT carry Lyme disease.
Habitat: Grassy and brushy areas more than forest. Common in meadows, trail edges, roadsides.
Active: June–August primarily, with activity starting in May in warm years. Range expanding northward.
Size: Adults 3–4mm. Females have a distinctive white dot (lone star) on the back.
Diseases: Ehrlichiosis, STARI, Alpha-Gal Syndrome (red meat allergy), Heartland virus.
Behavior: More aggressive than blacklegged ticks — actively pursues hosts rather than waiting on vegetation.
Lone star tick bites can trigger alpha-gal syndrome — an allergic reaction to red meat (beef, pork, lamb) that develops weeks after a bite and can be permanent. Cases are increasing in Rockingham and Strafford counties. If you develop allergic reactions after eating red meat, mention recent tick bites to your doctor immediately.
Dover, Portsmouth, Rochester, and Somersworth sit in one of the highest tick-density zones in New England. This isn't random — specific geographic and ecological factors make Seacoast NH yards more hazardous than the NH state average.
NH DHHS Lyme disease surveillance consistently shows Rockingham and Strafford counties — the heart of Seacoast NH — reporting among the highest per-capita Lyme case counts in the state. The combination of coastal wetlands, suburban forest fragmentation, high white-tailed deer density, and a warming climate that extends the tick season has made this region a persistent Lyme hotspot for over a decade.
The suburban-woodland interface that defines most Seacoast NH neighborhoods is precisely the habitat where tick density is highest. Ticks don't thrive in open grass or deep forest — they thrive at edges: where your lawn meets the tree line, around stone walls, in leaf litter under shrubs, and in ornamental plantings that border wooded areas. The typical Seacoast NH half-acre lot with a wooded back edge is ideal tick habitat.
The first 9 feet from the woodland edge to your lawn is where 90%+ of tick encounters happen on residential properties, according to tick ecology research from the University of Rhode Island. Professional yard treatment targeting this transition zone — along with leaf litter management and stone wall edges — addresses the actual habitat rather than broadcast-spraying the whole lawn.
Knowing the tick calendar is only useful if you act on it. Here's what the season requires from you — by quarter — to maintain meaningful protection for your family and yard.
The answer for Seacoast NH is mid-April. Waiting until Memorial Day means you've missed weeks of peak nymph activity. Treating in April is prevention — you're building a barrier before the highest-transmission window. Treating in June or July is reaction — ticks have already been active in your yard for weeks.
A three-treatment season plan (April, July, September) provides the best protection through the full NH tick season. If budget allows only one treatment, make it April. The ROI on early treatment is higher because you're protecting through May and June — the months that generate the most Lyme cases in Rockingham and Strafford counties.
Schedule a Free Yard InspectionThe questions Seacoast NH homeowners ask most often about when ticks are active and when to protect their yards.
Yes. Blacklegged ticks (deer ticks) become active once temperatures consistently exceed 40°F — which in NH typically happens in late March to early April. By mid-April, adult blacklegged ticks are fully active, and the first nymphs of the year begin emerging. April is the window to schedule your first yard treatment before nymph season peaks in May.
No. Ticks enter a dormant state under leaf litter and snow cover, where ground temperatures stay above freezing. Blacklegged ticks in particular can survive NH winters and emerge on any day above 40°F. This is well-documented — reports of active ticks in December and January during mild spells are common in Seacoast NH. Ticks are waiting, not dead.
Mid-April to early May for your first treatment — before nymph season peaks. The goal is to have the barrier in place before May, which is the highest Lyme transmission month. A follow-up treatment in early July and a third in September extends protection through the full NH tick season, including the October adult peak. If you can only do one treatment, make it April.
May and June are the highest Lyme-risk months in NH due to nymph tick season. Nymphs are poppy-seed sized (1–2mm) — nearly impossible to spot — and carry Lyme at adult rates. Their peak activity coincides exactly with peak outdoor family activity in the spring. October is the second-highest risk month due to the fall adult blacklegged tick surge.
Yes. Adult blacklegged ticks have a secondary activity peak in October and November in NH — fall activity is comparable to spring activity in intensity. NH DHHS Lyme surveillance data shows cases attributed to October exposure across Rockingham and Strafford counties every year. Many residents contract Lyme in fall after dropping their guard following summer. October tick checks are as important as May tick checks.
Lone star ticks are active primarily June through August in Seacoast NH, with activity starting in May in warm years. Their range has been expanding northward through Rockingham and Strafford counties. Unlike blacklegged ticks, lone star ticks actively pursue hosts rather than waiting on vegetation — they're more aggressive. They can cause alpha-gal syndrome (red meat allergy) and ehrlichiosis.
American dog ticks peak in May and June in NH, then decline significantly in summer heat. They prefer grassy and brushy areas over forest, and are much larger than deer ticks — adults are watermelon-seed sized (5–6mm) with distinctive white or silvery markings. Dog ticks do not carry Lyme disease, but can transmit Rocky Mountain Spotted Fever (rare in NH) and tularemia.
The tick calendar is relentless — nine months, two peak periods, three species, and a suburban yard that happens to be prime habitat. Trying to manage this with personal checks and repellent alone is exhausting and insufficient. A seasonal yard treatment program builds the barrier so your family can use the yard from April through November without calculating risk every time the kids go outside.
We'll walk your property, identify tick hotspots, and give you a clear quote for professional protection. Serving Dover, Portsmouth, Rochester & Somersworth NH.
A free yard inspection shows you exactly where your property's tick risk is concentrated — the lawn-woodland edge, leaf litter zones, stone walls — and what it costs to eliminate it. No obligation, no pressure. Serving Dover, Portsmouth, Rochester, and Somersworth NH.