Fleas are a problem year-round in warmer climates that rarely dip to the freezing mark, but some pet owners welcome colder weather because they believe it kills the pests. Unfortunately, that's not necessarily true. Extended freezing temperatures can kill fleas, but they have found ways to survive in cold climates.
Lowest Survivable Temperatures
It doesn't need to be quite freezing, or 32 degrees Fahrenheit, for fleas to freeze. Once the temperatures fall to 37 degrees, it's cold enough to kill mature fleas as well as eggs, larvae and pupae.
Freezing Temperature Durations
Fleas and their young don't die overnight when temperatures dip toward freezing. It can take up to 10 days of sustained 37-degrees-or-lower weather. If daytime highs exceed 37 degrees, the fleas might warm up enough to hang in there even longer. But when the weather maintains 37 degrees or colder all day and night for about 10 days, any fleas left outside and exposed will die.
How They Survive
Since fleas are still a problem even in the coldest areas of the country, it's obvious not all fleas die when temperatures drop. Some fleas are crafty enough to find ways to stay warm, including those living on wild animals such as raccoons. A sufficient number of eggs remain on the animals to keep the flea population alive until it can boom again in the warmer temperatures of spring. Other fleas find cozy areas in barns, garages and outdoor kennel bedding or under decks and around foundations to hide in and wait for warmer weather, or an unsuspecting animal, to arrive.
What You Can Do
Even when temperatures are freezing, you can end up with a flea problem in your home. Your pet can brush close enough by a flea's hiding place to allow the flea to hitch a ride inside. Or, you could pick up eggs or larvae in your shoes as you walk through your yard or outbuildings, then track them into your house. These fleas thrive in the warmth of your home, multiplying quickly into a problem, even in winter. If you notice fleas in your house, vacuum immediately and daily for a couple of weeks. This is one of the best ways to remove fleas and their eggs from your carpet, but dump what the vacuum picks up in a sealable plastic bag to keep the fleas from escaping from the garbage. Treat your pet with a vet-approved flea treatment.