Adult cat fleas die in temperatures colder than 46.4°F (8°C), and hotter than 95°F (35°C). However, the low-end extreme for immature fleas is 55.4°F (13°C). During winter, adults can survive in cold temperatures while living on a warm-bodied host.
Img 1 Environmental conditions needed for all life stages of the cat flea to survive.
Cat fleas can survive from egg to adult in temperatures between 55.4°F and 95°F (13°C and 35°C) Fig 1.
Temperatures below freezing are lethal to adult fleas . They’ll die within five days at 30.2°F (-1°C) Fig 2. At 24 hours, there’s mortality in 20% of emerged adults and 72% of pre-emerged adults. Fleas can live up to ten days at 37.4°F (3°C). Survival significantly increases when temperatures exceed 46.4°F (8°C), where nearly half of emerged adults stay alive for 20 days.
Fig 2 Percent of emerged adult fleas that survive (y-axis) across 40 days (x-axis).
Flea eggs and larvae are more susceptible to cold temperatures than adults. The immature stages require temperatures of at least 55.4°F (13°C). At 50.4°F (10°C), eggs hatch within 12 days, but first instar larvae die 10 days later.
In the winter, near-freezing temperatures kill fleas living outdoors. While frost kills fleas, not all will die in winter. Some immature stages develop in the freeze-protected dens of wild animals. Adults will survive on their warm-bodied hosts, such as dogs, cats, raccoons, or opossums. And, of course, fleas living within heated homes will survive.
Img 1 Fleas can survive winters indoors, in animal nests, or on warm-bodied hosts (e.g. raccoons).
Some geographic locations year-round warm and humid climates. As a result, fleas can thrive nearly all year long. In Florida, for instance, fleas continue developing even in the winter months from November to March.
Any temperature above 95°F (35°C) is lethal to adult fleas. They’ll die within two days unless relative humidity exceeds 75% Fig 3. Fleas can’t survive outdoors when temperatures surpass 95°F for more than 40 hours a month.
Fig 3 Days it takes (y-axis) for 90% of unfed adult fleas to die at various relative humidity percentages (x-axis) while temperature is kept constant at 95°F.
Washers and Dryers
Fleas, of any stage, can’t survive the laundering process. To kill fleas on clothing and bedding, it’s recommended to wash the items for 10 minutes at 140°F, and then dry at the highest heat setting. Multiple factors will prevent survival. They’re exposed to extreme heat, extreme dryness, flooding, detergents, and physical tumbling action.