Ticks are common outdoor pests, raising concerns about their activity in colder months. Many assume these arachnids disappear completely in cold weather, but this is a misconception. While activity levels change with weather, ticks adapt to endure cold, remaining a threat.
How Ticks Survive Cold Weather
Ticks employ several biological strategies to survive freezing temperatures. One key mechanism is entering a state of dormancy, a period of suspended development that conserves energy. This allows them to wait out unfavorable conditions, reducing their metabolic rate.
To endure the cold, ticks often seek shelter in insulated environments. They burrow into leaf litter, soil, or mulch, which provides a protective layer against extreme surface air temperatures. Snow cover also insulates, shielding ticks from freezing temperatures and cold winds. Some tick species produce “antifreeze-like” compounds, preventing ice crystals from forming in their cells. Additionally, ticks can reduce the water content in their cells to avoid freezing.
Temperature Thresholds for Tick Activity
Tick activity is strongly influenced by temperature, though exact thresholds vary by species and life stage. Blacklegged ticks become inactive below 35°F (1.7°C). However, they quickly resume activity when temperatures rise, even slightly above freezing. Adult blacklegged ticks are active and seek hosts at 4°C (39°F) or above.
While freezing temperatures can cause some tick mortality, many ticks can survive significantly colder conditions. Blacklegged ticks can survive temperatures as low as -7°F (-21.7°C) by drawing water out of their cells. American dog ticks and Lone Star ticks become inactive below 40°F (4.4°C), remaining dormant during colder winter months. Activity is not the same as survival; ticks can survive cold periods while remaining dormant, only to become active again when conditions improve.
Beyond Temperature Other Factors
Beyond air temperature, several other environmental factors influence tick survival and activity in cold weather. Snow cover provides an insulating effect, preventing ground temperatures from dropping below freezing. This subnivean space beneath the snow acts as a refuge, protecting ticks from harsh conditions.
Humidity levels are also important for tick survival, as ticks require moisture to prevent desiccation. In dry conditions, ticks remain concealed within leaf litter, emerging only when humidity is higher. Microclimates offer ticks warmer, more humid conditions compared to ambient air, allowing them to persist. Sun exposure can also influence local temperatures within these microclimates, potentially warming areas enough for brief periods of tick activity.
When Ticks Become Active Again
As winter transitions to spring and temperatures consistently rise, ticks begin to re-emerge from their overwintering states. Blacklegged ticks become active again when temperatures climb above freezing, around 4°C (39°F). This re-emergence can occur as early as late winter or early spring, especially during unseasonably warm spells.
The timing of tick activity can vary by region, but blacklegged ticks are active from October through May, as long as daytime temperatures remain above freezing. Nymphal ticks become most active from May through July, while adults show activity in the fall and again in the spring. Given their resilience and ability to become active during warm winter thaws, ticks can be a year-round concern in many regions.