How a warmer winter changes a tick’s odds
Ticks do not spend winter actively searching for people. Many shelter in leaf litter or soil, where conditions are more stable than the air above them. Cold can kill exposed ticks, while snow may insulate those hidden below. A milder winter can therefore leave more ticks alive to resume activity when temperatures rise—but warmth alone does not determine survival. Ticks also need suitable moisture; hot, dry conditions can be harmful.
Survival is only one step in expansion
A surviving tick still needs a host, such as a mouse, deer, or bird, to feed and complete its life cycle. Those hosts, along with vegetation and habitat, help determine where a tick can establish itself. A longer period of seasonal activity may give ticks more chances to find hosts and may shift when people encounter them outdoors.
The disease risk also depends on the particular tick and the pathogens it carries. Lyme disease and Rocky Mountain spotted fever involve different tick species, so a change in one species’ range does not automatically mean both diseases will spread in the same way.
What changes for people
As tick populations become established in places where they were once uncommon, residents and health workers may have less experience recognizing local tick exposure. The practical consequence is not that every warm winter brings an outbreak, but that familiar seasonal boundaries can become less reliable: checking for ticks may matter in places or at times when people previously did not expect them.
