Flea eggs can’t survive outside during winter, as they’ll die when continually exposed to cold temperatures. The low-end extreme occurs at 55.4°F (13°C). At this temperature, half of the eggs will hatch within six days. But colder than this and there’s developmental failure and death. Flea eggs don’t go dormant.
Flea eggs cannot survive outdoors during the winter, even in above freezing weather. 55.4°F (13°C) is the lowest temperature flea eggs can bear. 50% of eggs will hatch within six days at this temperature. When temperatures drop below this threshold, the fleas will fail to develop.
It’s possible for some eggs to survive and hatch when continuously exposed to 50.4°F (10°C), but 100% of the first instar larvae will die within 10 days at this temperature. At 46.4°F (8°C), 45% percent of eggs will die within a day, 65% will be dead by day five, and all the eggs die by day 10. At 37.4°F (3°C), 65% of the flea eggs die within a day, and 100% die by day five Fig 1.
Fig 1 Percent of eggs that survive (y-axis) across 10 days (x-axis).
The cold, dry winter air will stop immature cat fleas from living outdoors in most temperate zones. Flea eggs don’t go dormant. However, it’s important to note that most domestic infestations occur indoors, not outdoors. Flea eggs can also survive in the freeze-protected dens of wildlife.