Fleas are a pet owner's nightmare. Flea season starts in the spring, usually in May, but intensifies in September, October and November. A lot of people think they're in the clear after that, assuming that fleas die in winter. The truth, however, is that you still have to worry about fleas year round. Here's why:
A flea's host
As long as it's warm enough, fleas can survive and eggs can hatch with or without a host. So if fleas entered your house when it was warm out, their eggs could still hatch and attach themselves to your dog later. But even in colder temperatures, fleas can stay warm enough on any host, including wild animals that pass through your yard. This can lead to flea eggs falling off these animals, hatching when it's warmer and then attaching to your dog.
A flea's environment
While most people do treat their dogs for fleas, not many treat their homes. Interestingly, much of a flea's life cycle can occur off of a host. And your home creates a more-than-suitable environment that makes it easy for fleas and eggs to survive. But you can do things in your home to help prevent fleas, such as frequent cleaning. You'll want to regularly vacuum as well as wash dog beds, toys and any bedding or linens your dog comes in contact with.
Pro Tip: Use hot water when washing items as it's typically more effective at killing any fleas or flea eggs.
However, even if fleas don't come inside your home where there's guaranteed warmth, they can still find places outside that are warm enough to survive (like under your house). In reality, it doesn't need to be much higher than freezing temperatures for fleas or their eggs to survive. This means areas with more mild winters are at a greater risk of year-round flea issues than those with harsh winters with several days below zero degrees.
All of this is why it's really important to regularly use preventative flea and flea egg treatments on your dog and house, no matter the season.