As the days get shorter and the temperatures drop, we cozy up inside our homes. Unfortunately, so do pests. Not surprisingly, we see an uptick in customer reports regarding bugs and rodents getting inside as cooler weather arrives, so we decided to take some time to tell you why this happens. As the weather turns cold, bugs go into hiding, seek shelter indoors, or become dormant in protected outdoor spots to survive the winter. In this blog post, we’ll explore why cooler weather drives pests indoors and share practical tips to help you keep them out. Plus, we’ll explain how Miller HomePro 365 can provide extra protection to help homeowners in Des Moines, Kansas City, Omaha, and our Midwest service area stay pest-free in the fall—and all year. Let’s jump right in.

Why cold weather brings pests in

When it gets cold out, we bundle up in our favorite hoodies or sweaters to keep warm. Insects and rodents don’t have that luxury; instead, many pests look for a warm place to hide from the cold. Of course, there are always exceptions, and not all pests have trouble with the cold. In fact, most insects have developed effective strategies to survive cold weather, such as entering a dormant state or finding sheltered microenvironments.

What do bugs do in the fall?

Insects are cold-blooded, so they don’t regulate a consistent body temperature. Their body temperatures fluctuate with the surrounding environment, meaning they are at the same temperature as the air or soil around them. Since they can’t regulate temperature, they can freeze. But long before they freeze, many insects start looking for warm places to congregate. This behavior is called thermotaxis. Insects rely on external sources of heat to survive cold weather, seeking out sun-warmed surfaces or sheltered spots. It drives them to start crawling on the sun-warmed sides of buildings, hiding under the bark of trees to shield themselves from the elements, and coming indoors. Changes in day length also signal insects to prepare for winter, triggering survival mechanisms before temperatures drop. After seeking shelter, some insects can endure long periods of cold by entering dormancy or using other survival strategies.

  • When an insect warms itself on your home’s exterior, it is in the perfect location to find its way indoors.

  • When an insect crawls underneath the siding, it can find rotted wood gaps and enter wall voids.

  • When an insect crawls into a tiny sliver of a gap around a window frame, it can get into the frame void and possibly find a way into a wall void.

  • When an insect crawls around in an entryway, it can feel warmth coming from gaps in weather stripping and door sweeps. These warm temperatures invite the insects indoors.

Some insects lay eggs in protected places to survive winter, ensuring the next generation emerges when conditions improve.

After thermotaxis, it’s important to note that only a few insects have special adaptations, like antifreeze proteins or shelter-seeking behaviors, to survive extreme cold. Some insects come indoors not only for warmth but also because they are attracted by available food sources. When insects freeze, winter temperatures and low temperatures trigger these survival behaviors. Cold weather can also impact insect populations, affecting their abundance and activity in the following seasons. Compared to some insects, other species may not survive cold weather due to a lack of such adaptations. The freezing process in insects involves ice nucleation and biochemical changes that help them avoid or tolerate freezing within their bodies.

How freeze tolerant insects and spiders handle the fall weather

As mentioned briefly, some pests are well-equipped to deal with cold weather. Spiders are a great example. Some have a natural antifreeze that protects them from freezing, and they survive winter outdoors by hiding in woodpiles and other sheltered areas. They also enter a hibernation-like state called diapause, which allows them to become nearly metabolically inactive and survive harsh winter conditions. Some species may not survive freezing temperatures, but their spiderlings in egg sacs can.

So, why do spiders come inside homes on cool days? They follow the insects. Spiders eat various insects, and when insects go into hiding, spiders get hungry. Their hunger brings them into your home on a cool fall night and the comfortable lodgings and ample food supply may keep them there.

Fall rodent activity in the Midwest

Rats and mice have fur to help them stay warm. They don’t hibernate in winter and are often active on cold nights, braving the cold to find a meal. So, why do they tend to get into buildings in the fall?

While rodents are resistant to cold because they have fur, they are warm-blooded and tend to go where the temperatures are ideal. When temperatures start to cool, rodents know that winter is on the way. They will establish themselves if they find a food source inside a structure. They’ll eat human food as well as bugs.

Some rodents prefer to live in structures even if they don’t find a food source. A wall void is similar to a tree cavity or log, where they live in nature.

As you can see, fall is an important time of year to ensure your home is impenetrable to insects and rodents. This can save you the hassle of battling pests throughout the long winter.

Overwintering sites and insect survival

When cold weather hits, many insects rely on specialized strategies to survive the winter months. One of the most important tactics is finding overwintering sites—protected spots where they can escape extreme cold temperatures and freezing conditions. These sites can be almost anywhere: under layers of leaf litter, deep in the soil, tucked beneath tree bark, or even inside human structures like crawl spaces and attics. By seeking out these sheltered environments, insects can avoid the harshest temperature extremes and conserve energy until temperatures begin to rise again.

Different insect species have evolved unique ways to handle cold winter weather. Freeze tolerant insects, such as the woolly bear caterpillar, can actually survive ice formation within their bodies. They produce special proteins and anti-freeze compounds that lower the freezing point of their body fluids, allowing them to survive ice crystals forming inside them during extremely cold temperatures. On the other hand, freeze avoidant insects, like monarch butterflies, take a different approach—they migrate south to avoid cold temperatures altogether, spending the winter in warmer climates before returning when warm weather returns.

Many other insects, including bed bugs and stink bugs, survive the winter by seeking shelter in protected areas. These pests often find their way into homes, wall voids, or attics, where they can ride out the cold in relative safety. Beneficial insects, such as honeybees, cluster together in their hives to generate body heat, helping the colony survive even when air temperatures outside drop well below freezing.

Some species, like Japanese beetles, overwinter in the soil. The insulating properties of soil help them survive extreme cold, and as temperatures warm in spring, they emerge to start the next generation. The ability of an insect to survive freezing temperatures often depends on the freezing point of its body fluids and its supercooling point—the temperature at which its fluids will freeze. Many insects produce anti-freeze compounds to lower this point, increasing their chances of surviving the winter.

Understanding where insects go and how they survive during cold weather is crucial for effective pest management. By identifying common overwintering sites—such as leaf litter, soil, tree bark, and even inside homes—property owners can take steps to reduce pest populations before they become a problem. Targeting these areas with preventative treatments can help kill insects before they emerge in spring.

In summary, insect survival during cold winter weather is a complex process involving freeze tolerance, freeze avoidance, and the use of overwintering sites. As temperatures drop, many insects seek shelter and enter a hibernation state, waiting for the return of warm weather. By understanding these survival strategies, homeowners and pest professionals can better predict pest activity and protect their properties all winter long.

How to keep pests that seek shelter out during cooler weather

Only a handful of factors motivate pests and bring them inside. Some are beyond your control. For example, you can’t do anything about insects congregating on sun-warmed exterior surfaces. However, taking the time to address what you can control will impact pest activity near your home.

Remove overwintering sites and attractants

Inspect your exterior and consider what would attract insects, spiders, or rodents to live near your home.

  • Clean trash receptacles and keep all trash stowed and covered.

  • Keep exterior lights off or replace white lights with yellow, insect-resistant lights.

  • Remove leaves, branches, and other organic yard debris.

  • Pick up old tires, tarps, wheelbarrows, and other items that offer shelter to pests.

  • Trim vegetation to remove hiding places.

  • Move bird feeders away from your exterior.

  • Rake up nuts or fruit.

  • Properly store outdoor patio furniture.

Eliminate moisture and water sources

Pests need water to drink and to maintain body moisture. Addressing dampness, humidity, and water sources will help reduce pest activity.

  • Rake out your gutters to remove clogs and ensure downspouts divert water from the foundation.

  • Repair damaged areas of your gutter system.

  • Fix leaking spigots or exterior pipes.

  • Apply gradation or a French drain to address puddles and pooling.

  • Address indoor plumbing issues.

Seal entry points

Pests get into your home because they can. Everything you do to keep them out will help deter them.

  • Replace damaged weatherstripping and screens.

  • Caulk around door and window frames.

  • Fill in gaps around pipes, wires, and other exterior wall penetrations.

  • Apply vent covers or screens.

  • Fill in structural cavities.

  • Replace rotting wood.

Don't forget to sign up for year-round home pest control!

You can get a lot done with your DIY pest prevention efforts. But, for extra protection or if you’ve already detected pest activity in your home or property, Miller Pest Solutions can help!

Miller HomePro 365, one of our year-round home pest control plans, is designed to provide ongoing protection against pests, including insects, spiders, and rodents.

With Miller HomePro 365, you’ll receive regular assessments and treatments tailored to your home’s needs. We use advanced techniques and eco-friendly products to create a protective barrier around your home, preventing pests from entering. It is an easy and stress-free way to keep pests out. Check out the plan details and pricing below, or give us a shout!