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In California, warmer weather can bring unwanted visitors to your home or business.
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Cockroaches thrive in both indoor and outdoor environments where they can find food, water and shelter, according to the University of California’s Statewide Integrated Pest Management Program.
During the day, roaches hide in warm, dark, moist areas such as cracks, water meter boxes, sewers, and crawl spaces, according to pest management program.
They come out at night to feed on a wide range of organic matter.
Here’s why the pesky pests come inside your home — and how to keep them out:
Which cockroaches are common in California?
In California, five species of cockroaches are commonly regarded as pests: German cockroach, brownbanded cockroach, oriental cockroach, American cockroach, and Turkestan cockroach.
According to the University of California pest management program, German cockroaches are the roach species most commonly found indoors in California.
“They prefer food preparation areas, kitchens and bathrooms, favoring warm, humid areas,” the program said. “Severe infestations may spread to other parts of buildings.”
You can spot these pets in apartments, houses, schools, restaurants, hospitals and warehouses — “virtually any structure that has food preparation or storage areas,” University of California experts said.
How to identify roaches
Cockroaches vary in size, color, and appearance depending on the species, but they generally share a few key physical characteristics, according to Terminix, a global pest management firm.
Here’s what to look for:
- Body shape: Flat, oval-shaped bodies with long antennae and six legs.
- Size: Half an inch to 3 inches long.
- Color: Reddish-brown to dark brown or black.
Many cockroaches have wings, but not all species can fly.
What are health risks related to roaches?
Cockroaches don’t usually bite, but their presence in your home is related to a myriad of health risks.
Roaches spread more than 33 kinds of bacteria, including salmonella and E. coli, according to American Pest Solutions.
“This is because they crawl around in or on dumpsters, trash cans, bathroom areas, sewers, compost piles, dead animals and other dirty places where bacteria can be found,” the pest control company said.
Roaches also spread viruses including poliomyelitis, which causes polio, as well as parasitic worms.
In addition, the presence of roaches can trigger asthma, American Pest Solutions said.
Cockroaches can also contaminate food if they come into contact with it, spreading food-borne illnesses, according to a 2020 study.
How does drought affect cockroach behavior?
All pests need water to survive, and some need it more than others.
As of Thursday, Aug. 13, about 65% of California was experiencing “abnormally dry” conditions, according to the U.S. Drought Monitor.
About 6.5% of the state — mainly Del Norte County — was in moderate drought, the drought monitor map showed.
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Water is the primary reason cockroaches head indoors during dry weather, according to Pest Control California, which is headquartered in California.
A cockroach can survive more than a month without eating food.
“However, it will die of dehydration in less than a week if it does not have access to water,” Pest Control California said..
Does wet weather increase roach activity?
Wet weather triggers a “noticeable surge in cockroach activity” indoors, according to Essential Pest Control.
“This is primarily because heavy rainfall can flood the insects’ outdoor habitats such as sewers, gutters and underground nests, forcing them to seek shelter elsewhere,” the Arizona-based pest control company said.
Homes and businesses offer “stable temperatures, food sources and moisture-free zones, making them prime targets during storms,” Essential Pest Control said.
What’s the worst time of year for roaches in California?
“Every season is roach season in California,” A-Z Animals said.
“Californians don’t get a break from these bugs in the winter and fall” due to the state’s relatively mild climate, the educational website said.
“If temperatures indoors stay above 50 degrees, roaches can be active year-round,” A-Z Animals said.
What are key signs of a cockroach infestation?
According to Western Exterminator, cockroaches excel at staying out of sight.
However, the bugs leave traces behind.
The Anaheim-based pest control company advises looking for these key “warning signs” to tell if you have a cockroach infestation:
- Droppings: Small, dark pellets or smear marks near baseboards, under sinks and behind appliances
- Egg cases: Small, brownish capsules in hidden areas near food sources
- Shed skins
- Musty odor: A distinctive, unpleasant smell that intensifies as an infestation grows
- Live or dead cockroaches during the day
How do I keep roaches out of my home?
Cockroaches are among the “most resilient pests in the world,” according to the National Pest Management Association.
The insects’ “unique survival tactics” include the ability to live for a week without heads, the nonprofit organization said, making eradicating them a difficult task for homeowners.
“Good sanitation and exclusion are important for effective control,” the Statewide Integrated Pest Management Program said. “Pesticides alone will not solve cockroach problems.”
The National Pest Management Association recommends these tips to make your home less inviting for cockroaches:
- Keep counters, sinks, tables and floors free of clutter and crumbs.
- Don’t let dishes pile up in the sink or spills stay on the counter.
- Store food in airtight containers.
- Avoid leaving out pet food.
- Vacuum at least once a week to remove food particles.
- Ventilate crawl spaces to prevent moisture buildup.
The National Pesticide Information Center suggests taking these steps to take control of a cockroach infestation:
- Locate as many active hiding places as possible.
- Look for warm areas with access to water.
- Use sticky traps to identify areas of high cockroach activity.
- Get rid of clutter that cockroaches might use for hiding and breeding.
If you decide to use pesticides, choose the least toxic options first and always read and follow label directions carefully, experts say.
This story was originally published August 15, 2026 at 5:00 AM with the headline “Drought and rain draw cockroaches inside your CA home. How to keep them out.”
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