Cold weather is often believed to eliminate pests like cockroaches. However, species such as the German cockroach (Blattella germanica), American cockroach (Periplaneta americana), and Oriental cockroach (Blatta orientalis) have developed distinct survival strategies for cold conditions. Understanding their winter behavior is important for homeowners because dropping outdoor temperatures do not end the infestation threat. Instead, the change in season often shifts their activity from the outdoors to protected spaces within human dwellings.
How Roach Activity Changes When Temperatures Drop
A cockroach’s activity level during winter depends on whether it is part of an outdoor or indoor population. Cockroaches are cold-blooded (ectothermic), meaning their body temperature mirrors their surroundings, and their metabolism slows significantly when cold. Outdoor cockroach activity drops sharply when temperatures fall below 50°F, causing them to become sluggish and less mobile.
Outdoor species, such as the American or Oriental cockroach, seek sheltered microclimates like sewer systems, deep mulch, or decaying logs to avoid the cold. If they cannot find adequate shelter, prolonged exposure to temperatures below 15°F is lethal for most species. This cold-induced inactivity is called quiescence, where movement and reproduction cease until warmer conditions return.
In contrast, the activity of indoor populations, particularly the German cockroach, remains constant year-round. These pests rely on the stable warmth and abundant resources found inside heated structures. The constant indoor environment, often maintained between 70°F and 85°F, allows them to continue foraging and reproducing. Sightings may even increase indoors during the fall and winter as outdoor populations migrate inside for refuge.
The Biology of Cold Survival
Cockroaches possess physiological mechanisms that allow them to endure cold temperatures. One survival strategy is diapause, a state of suspended development distinct from true hibernation. Diapause is triggered in nymphs or eggs by decreasing temperatures or shortening daylight hours, halting growth and conserving energy until spring.
For colder-tolerant species, the body synthesizes cryoprotectants, which act as a natural antifreeze to prevent ice crystals from forming inside cells. These substances, including glycerol and the sugar trehalose, are concentrated in the insect’s hemolymph (blood), lowering its freezing point. This process is a form of freeze avoidance, allowing the cockroach to survive temperatures that would otherwise cause lethal intracellular freezing.
Some species, such as the New Zealand alpine cockroach, exhibit freeze tolerance by regulating the freezing process so that ice forms in less harmful extracellular spaces. However, most pest species are not truly freeze-tolerant, and temperatures below 15°F will kill them without the protection of shelter. Their cold tolerance helps keep them alive while seeking a permanent, warmer harborage.
Prime Winter Harborages
When the weather turns cold, cockroaches seek microclimates that replicate their preferred warm and humid conditions. Indoors, the most attractive harborages are areas that generate consistent heat and offer moisture, maintaining temperatures of 70°F to 80°F. These locations include voids behind and beneath heat-producing appliances like refrigerators, stoves, and dishwashers, where motors provide constant warmth.
Cockroaches also congregate inside walls near hot water pipes, behind hot water heaters, and around furnace ducts, exploiting thermal leakage from these utility systems. Kitchen cabinets, especially those beneath the sink, offer warmth, darkness, and moisture from plumbing leaks. These pests utilize small cracks, crevices, and utility entry points to access wall voids and sub-flooring for nesting.
Outdoor species, such as the American and Oriental cockroaches, will migrate to sheltered, semi-outdoor locations if they cannot enter the main structure. These harborages include basements, crawl spaces, and utility tunnels where temperatures remain above freezing. They also thrive in urban sewer systems and floor drains, where constant moisture and warmer temperatures provide year-round refuge.