What Time of Year Are Ticks Most Active?

NH DHHS guidance is direct: ticks are active any time the outside temperature is above 40°F and they're not covered by snow, with peak activity from April through November. That's a much wider window than most people assume, and it means a mild stretch in late fall, an early spring thaw, or even an unusually warm winter day can bring ticks out when someone isn't expecting them. Tick awareness in New Hampshire is realistically a year-round habit, not a seasonal one.

Nymphs — the poppy-seed-sized immature stage of the blacklegged tick — are responsible for the majority of human Lyme disease cases, largely because they're so small and easy to miss during a tick check. Their activity peaks roughly May through July in the Northeast, which makes late spring and early summer the single highest-risk stretch for a human tick bite that goes unnoticed long enough to matter for disease transmission.

Adult blacklegged ticks follow a different rhythm: they're most active in spring and again in fall, and unlike many insects, they don't hibernate through the cold months. TickEncounter notes adult blacklegged ticks are active 'October–May, as long as the daytime temperature remains above freezing' — meaning a warm winter day can genuinely bring adult ticks out questing, even in January or February. Adults are also a notable disease-transmission concern precisely because that's when they're most likely to be encountered, sometimes when people have let their guard down.

Because nymphs and adults peak at different times of year, effective prevention isn't a single seasonal push — it's sustained through most of the year. Yard treatment timed to the nymph season (late spring into early summer) targets the highest-risk life stage, while pet prevention products, per CAPC guidance, are generally recommended year-round rather than seasonally, since adult ticks can still be active on warm days well outside the traditional 'tick season.'