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Ooooh, that smell! Odors rise with the temperature

A pile of trash sits on the curb in New York City on Wednesday. John Brecher / NBC News

Your nose doesn't lie - odors intensify in the warm summer months, be they of rotting garbage on the sidewalk or fragrant flowers blooming in a garden.

The combination of heat and humidity allows bacteria to grow faster and smells to travel farther, said Victoria Henshaw, who researches urban smells throughout the world.

“The air becomes a smelly soup that we all breathe in,” Henshaw said.

Unfortunately, rotten aromas trump pleasant scents when it's hot, allowing the odor of pollution to travel farther and overpower fruity smells or freshly cut grass.

Humid air traps smells and causes them to linger longer than they usually would, said Avert Gilbert, a smell psychologist. He said it’s not just an intensification of already-present odors like urine and garbage that makes summer’s stinkier.

“Stores open up, restaurants open their doors,” he said, “There’s just more smells pouring into the streets than on a brisk fall day or a cold winter.”

That means when the fish market owner dumps the ice into the drain, it’s going to fill the air more in the summer than on a cooler, fall day.

Certain smells can fill a room, like cinnamon or popcorn.

“If someone’s mulling wine in your kitchen, it will fill the whole house,” Gilbert said. “If you walk by a movie theater, the smell of popcorn surrounds you.”

Henshaw takes people on smell walks all across the world, where she said people are more willing to smell things they would normally turn their noses up to.

“With great gusto, people will go up and sniff the trash,” she said.

The humans' sense of smell evolves over their lifetimes. In fact, as babies, humans gravitate toward the smell of feces because it is something they are familiar with, Henshaw said. It isn’t until babies get older that they realize it’s not a good smell, she said.

Since smell is part of our olfactory senses, many people associate certain smells with people or areas. Henshaw said humans have the ability to remember a smell for more than 60 years.

“Our mind just takes us back to that space and time,” she said. “That’s why smell has such an association with certain cities.”

Odor experts agree New York City is the most infamous for its summer stench, but other major cities like Philadelphia and San Francisco suffer from the same problem.

“It smells like a petting zoo carefully adorned with hot, wet garbage and the subtle hint of pee pee,” said New Yorker Stefania Orru of the city’s intense summer smells.

The city’s smells aren’t going anywhere soon, so Henshaw said she recommends embracing the smells and getting used to them. That, or buying a scented handkerchief drenched with your favorite perfume.