When It Rains, It Pours Pests - Part 1

Ants on a wet branch holding up a clover after it rained.

For many areas in the country, autumn means the arrival of a steady rain pattern. Rain in the fall and winter is much different than in spring and summer, as there is the addition of cooler temperatures and fewer daylight hours. It seems like this should be the time when we experience the least amount of pest problems, right? Unfortunately, this dream is not a reality. Plenty of pests would love the chance to invade our homes for the shelter from the storm and for food sources, but there are certain species that seem to be more common than others.

Let’s look at four different pests that also like the cozy feeling of a rainy day, but for much different reasons than we do. Make sure to return next week for part two, where we discuss four more pests that like to make their presence known during a rainstorm!


How to Keep Pests Out

Before we discuss the pests, it would help to give some advice on how to keep them out in the first place. Sealing all cracks and gaps in the house is a great start, and is a constructive task to do year-round. This is the main way that pests enter our homes, so taking it away will greatly help to reduce the amount of pests. Caulk is sufficient for cracks, and copper mesh is often the best tool for gaps and holes. Also, cleaning out gutters before the storm arrives is a good idea in general. This not only helps to keep your house leak-free and keep the rain water draining properly, it also takes away a hiding place of pests. Finally, check for any wood damage or preexisting structural issues in the house or yard. These will only get worse with a bad rainstorm, so we recommend looking into repairs or anything that needs to be done ahead of time.



One roach crawling on the wall


It only seems reasonable that one of the worst, if not the worst, pests is also a potential problem during a rainstorm. Cockroaches are expert hiders, nocturnal scavengers, and loaded carriers of countless diseases and harmful pathogens. Much of this is due to their preferred habitat, which is how they end up in this position in the first place. Roaches like to live in damp pipes and sewers because they have the three necessities of life for insects: food, water, and shelter. A major rainstorm can cause the pipes and sewers to flood to an extent, which forces the roaches out of their disgusting homes. They seek dry areas safe from the dangerous rainwater, which usually means the place that these pipes and sewers lead to or are near. Roaches can climb up the pipes and follow them to the surface. This is why they are also found near drains and showers, so our bathrooms, kitchens, and laundry rooms may see some roaches after a major rain storm.

Since roaches are nocturnal, they can remain hidden for quite a long time from us. Of course, the droppings, gnawed materials, and skin castes are plenty of evidence that they are in the area. Roaches are also positively thigmotactic, which means they can compress every part of their bodies to fit in the tightest of spaces. They may initially invade just to escape the floodwaters from the storm, but if they find food sources and moisture in isolated areas, they may stick around and reproduce in their new home.



Centipede on a leaf


This is one of the most common moisture-loving pests year-round, but they are especially prevalent during the rainy season. Centipedes tend to stick with humid and moist areas since they require a certain amount of steady moisture to survive. This makes it seem like they would love to be outside during the rain, but that is not where their food source is anymore. Centipedes live off of smaller insects, like roaches and crickets, which are most likely seeking shelter at the moment. As long as centipedes can find moisture in their new habitat, they will happily move wherever they can find reliable food and water.

Centipedes can enter through any kind of opening in the house or building, as their many pairs of legs help them to slink through unnoticed. The common openings include holes in screens, vents, and gaps around the garage door. They will stay in the bathrooms, garage, and/or basement once inside, since those are the places they are most likely to receive constant moisture. Centipedes are also blind, which means they find their prey by feeling with their antennae and detecting the location of their prey. If you see a centipede in your home, chances are high that there are other insects in the area.



Large ant on a wet leaf


Surprisingly, the main reason that ants invade during a rain storm is not simply because of food. Since this seems to be their driving force for living, it feels like this would still be their main focus. But it is actually because their home is in danger of being destroyed, if not totally wiped out. Ants of various species like to construct their nests in the dirt, resulting in the mounds that we call “ant hills.” This provides great protection during a sunny day, but the rain is a different story. Their mounds will flood and wash away the colony if they are not careful, which is why they search for better shelter as soon as they sense the change in atmospheric pressure.

Ants then look for any kind of dry land on an elevated position, as having the high ground here means the difference between survival and expiration. They will use any cracks and gaps they can find in our homes, like near the big garage door, slider doors, and in the foundation. Once they set their sights on dry land, they will resume their search for food. The worker ants forage for anything they can, leaving pheromones for the rest of the colony to follow to the food. If the food is reliable and they can rebuild a nest in the dry area, the ants will stay in their new home for as long as they can. This means that if they happen to get into our kitchens, they could happily stay there forever and have more food than they could ever dream of.



Spider web in a tree branch, soaked with rain


Spiders are generally less of a threat because they do not invade in numbers, unless you have a mother spider with her whole brood on your hands (oh, the horror!). They are similar to centipedes in that they also go where the food is reliable and enjoyable. The main difference between them is that spiders like it to be as dry as possible, which is another main motivation for moving inside during a rainstorm. Spiders are possibly the most common indoor pest during fall and winter across the country because they are seeking out a warm and dry shelter that they can also feed in. Basically, spiders want all of their necessities in the same area so they don’t have to travel for anything. Talk about settling down!

Spiders can fit through any crack or gap, depending on the size of the spider. They like to be isolated from us and our pets, and will typically hide in corners, under appliances, and in closets. They eat a wide range of insects and small pests, which technically makes them beneficial creatures to us. But having a house full of spiders during a rainstorm does not sound like a fun activity on a rainy day, so we recommend sealing cracks and holes to keep the spiders outside with the food sources they can still find out there.

Rainy Season is Still Pest Control Season

Some people have been led to believe that the need for pest control services stops with the arrival of the fall season. After all, aren’t we taught that the peak of pest activity is summer? But the reality is that pests are active in some way year-round, as many of us who have experienced unfortunate pest invasions during cold weather know. The one caveat for pest control during the rainy season is that outdoor treatments cannot be applied right before or during a rain storm. It wouldn’t do much good to have a technician spray and lay down bait only for it to wash away before it has time to be effective!

But once there is a break in the rain and the forecast does not show another storm for at least a little while, it is a great idea to have pest control services in the meantime. Bel-O technicians know the best ways to utilize both preventative and responsive treatments throughout the fall and winter in order to leave you with a pest-free home year-round. We offer a free inspection of the home so you can learn exactly what pest is trying to make your home their own. Contact us to learn more about how our team can solve your pest issues before the next rainy day sets in!


How to deal with insects after a storm. (n.d.). Ortho. Retrieved October 14, 2022, from https://www.ortho.com/en-us/library/garden/why-does-bug-activity-increase-after-rain

What brings cockroaches inside after a heavy rain?. (n.d.). Terminix. Retrieved October 14, 2022, from https://www.terminix.com/cockroaches/what-brings-cockroaches-inside-rain/

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