Pest control professionals and researchers say a combination of heat and rain has created favorable conditions for insects, leading to increased activity later in the season.
The trend comes as Delaware County, Pennsylvania, investigates three probable human cases of West Nile virus.
Rich Foreman, owner of Dynamite Pest Control, said his company is receiving more service calls than usual for this time of year.
"Right now, we're in an Indian summer on our next heat wave and I'm very busy," Foreman said.
Foreman said the increase in business reflects a broader increase in insect activity.
Clayton Traylor, a Temple University post-doctoral researcher and entomologist, said warmer temperatures can significantly affect insect populations.
"Insects are really limited by heat. So the hotter it is, the more active they are, the faster they can reproduce," Traylor said. "And so when you have a really hot summer, insects are going to be more active like they were this summer."
According to Traylor, the combination of heat and rain has created ideal conditions for several pests, including ants, cockroaches and mosquitoes.
"They live in stagnant water, like pots that fill with water in their backyards," Traylor said of mosquitoes.
The growing mosquito population is of particular concern as Delaware County confirms it is investigating three probable cases of West Nile virus in humans.
Experts say insect activity is likely to continue until temperatures drop significantly. Traylor said bugs should begin slowing down after the season's first freeze.
"Maybe mid October, early November we'll finally get there," he said.
Homeowners can take steps to reduce pest problems by keeping spaces clean and eliminating standing water, both outdoors and indoors.
"Don't leave water in the sink. Dry off the dishes," Foreman said.
For those considering professional treatment, Foreman advised choosing a qualified company.
"Just make sure any pest control company you use is licensed, insured and also can pass an FBI background check," he said.
Foreman also noted that homeowners can help maximize the effectiveness of pest treatments by cleaning with mild soap and water, as bleach can make many extermination products less effective.
Until cooler temperatures arrive, residents may need to prepare for an extended season of increased insect activity.