It's hot out - watch out for flying cockroaches!

NEW YORK -- As if the hot weather isn't enough, it turns out heat makes cockroaches more likely to fly.

An expert explains why heat and cockroaches are not a good mix.

"The American Cockroach is the most commonly found flying," says Entomologist Louis Sorkin.

The American cockroach, they are generally unwelcome dead or alive. And no one wants to see one flying straight at them.

"They might not be going at you directly, but just flying in your direction and you're in their way," Sorkin said.

Sorkin explains how the heat and humidity causes them to come up from the sewer and subway at night and take flight.

"There's more activity when there's more heat, running, flying, fluttering," Sorkin said.

To the average person, who is not scientific at all, there's only one thing to say about flying cockroaches - Ew!

Flying roaches has even become a hashtag for sightings and reaction.

"Much of the flight though is running and taking off and fluttering down somewhere. On occasion you can actually see them take off from the ground and flutter and go up," Sorkin said.