Can cold weather make you sick? Experts explain why more people feel ill in the winter

Cold and flu season always comes around when the weather starts to change. But does cold, wet weather actually make you sick? Not really, experts say. But cooler temperatures and dry winter air can affect your body in surprising ways.

As the weather starts to turn, rates of certain respiratory illnesses start to tick up. Beginning in September and October, we might start to see more cases of rhinovirus (a frequent cause of the common cold) and influenza, Ellen Foxman, Ph.D., associate professor of laboratory medicine and immunobiology at the Yale School of Medicine, tells TODAY.com.

Early in the fall, experts might also see more cases of respiratory syncytial virus, Dr. Geeta Sood, assistant professor of medicine and epidemiologist at Johns Hopkins Bayview Medical Center, tells TODAY.com.

With COVID-19 in the mix, the dynamics of respiratory virus season have changed in the last few years, Sood says.

The seasonal flu usually causes a sharp rise in cases with a peak that lasts around two to three weeks, Foxman explains. "That's usually somewhere between Nov. 1 and March 1, but it's hard to predict exactly when," she adds.

Right now, flu rates in the U.S. are just starting to rise, Foxman says, so the peak may come sometime in December this year.

In general, illnesses like these all tend to have a wave in the fall and winter "because many of the same risk factors for influenza and RSV are also the same risk factors for COVID-19 infection," Sood explains.

Does cold, wet weather make you sick?

No. Cold or wet weather on its own doesn't cause a cold and won't make you sick, the experts say.

Can cold weather make you more likely to get sick?

It is true that respiratory viral illnesses tend to spike in the cooler months, Foxman says. But if the cold doesn't cause illnesses directly, what's causing the connection between cool weather and colds?

First, the cold winter air may actually make it easier for viruses to spread. "It's thought that the cooler, drier air helps (viruses like flu and SARS-CoV-2) transmit better from person to person," Foxman says.

And her previous work suggests that "changes in the ambient temperature (can affect) your body's ability to fight viruses," she explains. That research shows that even small changes in the temperature of your airways can negatively impact the tissues that line those airways, which typically act as the body's first line of defense against respiratory pathogens.

"If you happen to have a virus in your airway, having the lining of the airway be a slightly cooler temperature can promote the virus's ability to replicate because your body can't fight it off as well," Foxman explains.

There are also indirect factors to consider here as well, Sood says.

For instance, it's during these cooler months that school starts and we tend to travel and gather indoors with friends and family. Behaviors like these — especially when they're happening in confined spaces with little air flow — encourage viruses to spread, she says.

Can cold weather make you feel sick?

Even if you're not actually sick, there some very understandable reasons that the changing of seasons can make you feel a little off.

For instance, shorter daylight hours have an "impact on people's mental health and energy levels," Sood explains, and that can make you feel "run down."

Some people also experience fall allergies and have greater exposure to indoor allergens like pet dander and dust mites this time of year, Dr. Zachary Rubin, an allergist with Oak Brook Allergists and spokesperson for the American College of Allergy, Asthma and Immunology, told TODAY.com previously.

Fall allergies can cause similar symptoms to a common cold, such as congestion, post-nasal drip and fatigue, Rubin said.

Others also experience a condition called nonallergic rhinitis, a condition that causes allergy-like symptoms — stuffy, runny nose, for instance — that aren't related to allergies. Changes in temperature or humidity are common causes of nonallergic rhinitis, the Mayo Clinic says.

For some, weather changes can "create extra inflammation for people," Rubin said, which can cause us to feel out of whack and exacerbate allergy symptoms. “Think of it like your body has a set point that it’s used to,” he explained, “and when we have these dramatic changes, that could potentially (affect) how your immune system responds.”

How to stay healthy when the weather gets cold

Knowing that respiratory illnesses are circulating when the weather cools off, it makes sense to take some extra steps to keep yourself healthy — especially this time of year.

First off, consider getting vaccinated, Sood says. There are vaccines available to protect against COVID-19, seasonal flu and now RSV (for older adults) as well. "Vaccinations are truly miraculous in terms of preventing severe disease and, in some cases, any disease," Sood says.

Additionally, masking is still an effective way to protect yourself during the respiratory virus season, the experts say. And it's a really good idea to mask up during busy holiday travel, like plane rides, Sood says.

Wearing a mask or scarf over your face when outside in cold weather can also help "humidify your airway," Foxman says. "The air you're exhaling is warm and humid from inside your body," she explains, "and if you have a scarf or a mask over your nose and mouth, you're holding that warmth and humidity in your upper airway as you're breathing out."

Knowing that viruses may be more able to infect you if your airways are cool and dry, this strategy may help bolster your body's protection against those viruses.

At holiday gatherings, "make sure that you have as much circulation of good, clean air as possible," Sood adds, "so that even if you are around someone who's infected, it's less likely to spread." You can encourage better air quality by using HEPA filters and, if weather allows, opening some windows.

Consider taking an at-home COVID-19 test before attending a gathering — especially if you develop any symptoms that could indicate an infection.

And don't forget about basic self-care practices to boost your immune system, Foxman says. That includes getting good quality sleep, staying physically active, managing stress and eating a balanced diet full of immune-boosting foods, like fruits and vegetables.

Even if cold, wet weather doesn't directly cause a cold, take the change in seasons as a reminder that respiratory illnesses are likely to be circulating right now — and you have tools available to keep yourself and your community safe.

This story first appeared on TODAY.com. More from TODAY:

• Want to be more flexible? Try this 5-minute daily stretching routine
• Anthem Blue Cross Blue Shield 'will not proceed' with policy change that wouldn't cover anesthesia after certain time limits
• Ariana Grande reacts to public comments on her health and ‘what’s wrong’ with her