If you tend to get the sniffles the second the seasons start to shift, you might wonder, why do I get sick when the weather changes? Turns out, there’s research to explain why you always feel icky at these turning points in the calendar, especially as we head into the cooler months.

To be clear, a dip in temperature, in and of itself, is not the reason you’re more likely to catch a cold when it’s cold outside. Rather, weather changes can challenge your immune system, and this may predispose you to falling ill.

Here, check out the science-backed reasons you might feel particularly under the weather as we trade our flip-flops and bathing suits for sweaters and boots (and learn how to lower your risk during peak virus seasons). In the meantime, keeping this immune-system-boosting soup simmering on the back burner isn’t such a bad idea.

1. You have seasonal allergies

If you have seasonal allergies, you might get sick during weather changes more often than others. While allergies don’t “turn into” a cold, they make you more susceptible to sickness in a few ways.

For one, classic seasonal allergy symptoms like itchy eyes, sneezing, runny nose, coughing, and wheezing “can increase fatigue and interfere with sleep,” says Steven J. Kravet, MD, MBA, professor of medicine and president of Johns Hopkins Community Physicians. “This can impact the immune system and predispose [you] to more general illness.”

On top of a weakened immune system, “upper airway congestion can cause fluid to build up in sinuses and the ears,” Dr. Kravet says. Sometimes, if the fluid doesn’t drain well, it can develop into an infection, he says (hello, sinusitis).

Allergens change from season to season, but the major offenders in fall tend to be ragweed, mugwort, sagebrush, and mold, while the spring and summer are better known for tree and grass pollen.

Some people with pollen or weed allergies might also find their favorite seasonal fruits trigger symptoms as well, Dr. Kravet says. For folks with oral allergy syndrome (OAS)—also known as pollen food allergy syndrome (PFAS)—eating certain kinds of fruits or veggies triggers an allergic reaction as their immune system reacts to certain proteins in these foods.

2. Barometric pressure is bringing you down

If allergies aren’t a problem, swings in barometric pressure (aka, the air pressing down on your body), might be. “As seasons change, weather often becomes more labile. We may see more storms and fluctuations in temperature from day to day,” Dr. Kravet says. “These changes often bring about wide swings in barometric pressure.”

When air pressure fluctuates (especially when it drops), it affects your nasal and sinus cavities because these areas are essentially air channels, according to a March 2024 analysis in World Journal of Otorhinolaryngology-Head and Neck Surgery¹. Specifically, a sudden shift in barometric pressure can disrupt the balance of fluid in these cavities.

This “can impact us in a number of ways,” Dr. Kravet says, causing nasal congestion, ear pain, and headaches (yep, weather changes can trigger migraines).

3. You’re spending more time around other people

During the cooler months, we tend to spend more time inside. Kids go back to school, we gather for the holidays, and most of us hibernate in our homes as fall gives way to winter. Here’s the rub: “It is easier to transmit viruses when people are indoors in closer proximity,” Dr. Kravet says.

Along with more exposure to viruses, indoor ventilation is often inadequate, too, says Vani George, DO, assistant professor of medicine (infectious diseases) at Icahn School of Medicine at Mount Sinai. This factor also plays a big part in increasing transmissibility of viruses, which can lead to respiratory illnesses, Dr. George says.

4. Colder, drier air is lowering your immune system

As temps drop, so do our immune defenses. But why does colder air make you more vulnerable to viruses?

Cold air can be desert-dry. With every breath, it can dry out your mucus membranes, even cause cracks in them, according to a December 2021 review in Cochrane Database System Reviews². When this happens, viruses have an easier way to enter your body.

Frigid outdoor air isn’t the only problem, though. Odds are, your home’s heating system is also drying out your nasal passages, Dr. Kravet says. “Dryness in the nose can lead to congestion, and congestion can predispose [you] to sinus infections,” he says.

You may feen even worse if your heat and air filters are filthy. Dirty filters can harbor pollen, dust, mold, and mildew, which can trigger or exacerbate chronic sinus and throat issues, according to Piedmont Healthcare. To avoid this, most air filter manufacturers and HVAC companies recommend changing your air filters every 90 days. The Center for Allergy & Asthma of Georgia recommends changing them more often (every 20 to 45 days) if someone in your household has environmental allergies.

5. More viruses are circulating during these times

“Certain viruses are more common in specific seasons,” Dr. George says. Some germs thrive in different types of weather, especially when it’s colder. Case in point: “Influenza, for example, typically peaks in the winter months,” she says. “These surges of viruses in the community may lead to respiratory illnesses.”

6. You have underlying health conditions

Seasonal changes can predispose anyone to getting sick. But your risk for coming down with something when the weather changes is even greater if you have an underlying health condition. “Having a decreased immune system will make one susceptible to infections,” Dr. George says.

It makes a lot of sense. With an already weakened immune system, your body might have a hard time mounting a proper defense when the perfect storm of factors—like cold, dry air and increased exposure to viruses—comes its way.

Other symptoms to expect during season changes

When the seasons shift, allergy symptoms are pretty common. People with allergies typically deal with the following symptoms, per Yale Medicine:

• Congestion
• Sneezing
• Itchy eyes, nose, and throat
• Runny nose and eyes
• Post-nasal drip (i.e., drainage in the throat)
• Fatigue
• Coughing

If you’re thinking, a lot of these allergy symptoms overlap with the common cold, you’re spot on. Unfortunately, telling the difference can be tricky, Dr. Kravet says. Dr. George agrees: “Sometimes people may misconstrue their symptoms for allergies, when in fact, they might have a viral infection.”

While the distinction is difficult, there are a few key clues to help you distinguish between the two, Dr. Kravet says. Specifically, itchiness (itchy eyes, nose, throat) is a sign you’re dealing with allergies, while a fever is more likely to indicate a cold or other virus. You can also keep an eye on your local pollen levels—if your symptoms get worse when pollen counts are high, you’re probably dealing with allergies.

In the end, though, it might not matter all that much. “Whether symptoms are from a virus or allergies, we often treat them similarly with nasal steroids as well as oral and nasal antihistamines,” Dr. Kravet says. And to be safe, always wash your hands well and often to avoid spreading (or catching) germs.

When to see a doctor

If you’re unsure whether you have a cold or allergies, you might take a wait-and-see approach. Keep in mind, though: “Most viral infections last less than 10 days,” Dr. George says. If your symptoms persist longer than a week or worsen, check in with your doctor.

Likewise, it might be time to see your doctor “when symptoms progress beyond itchy eyes, runny nose, and congestion to include” the following symptoms, Dr. Kravet says:

• Shortness of breath or difficulty breathing
• Fever or chills
• Throat or ear pain
• Sputum (mucus from your lungs), particularly if it’s changing color

Tips for staying healthy as the seasons change

“We are best able to fend off viruses, manage our aches and pains, fight fatigue, and battle allergens when our immune system is not overwhelmed” during the changing of the seasons, Dr. Kravet says. While you can’t always skirt getting sick, there are a lot of things you can do to try to stay healthy when seasonal viruses peak.

1. Wear masks

While you may no longer mask like you did during the peak of the COVID-19 pandemic, it’s still a smart idea to have a few masks on hand. During flu season, wearing a mask indoors, especially when you’re around a lot of people, can help prevent you from picking up germs, Dr. Kravet says.

2. Stay warm

Heat escapes from your head, fingers, toes, ears, nose, and mouth, so keeping these body parts covered in cold weather is important for maintaining your body’s warmth and a healthy immune system, per Harvard Health Publishing.

3. Use a humidifier

This can add moisture to the air and help prevent dry nasal passages, Dr. Kravet says. Again, when your mucous membranes dry out and crack, they become easier entryways to viruses. (Check out the best portable humidifiers to amp up the moisture at home, at work, and anywhere else you spend time.)

4. Use a saline nose spray

Like humidifiers, saline nose spray is a safe way to keep your nasal cavity moist, Dr. Kravet says.

5. Eat nutrient-dense foods

A balanced diet, like the Mediterranean diet, that involves eating an abundance of fruits and veggies can support your immune system. In fact, an August 2024 systematic review in PLOS One³ found that following the Mediterranean diet may lower your risk of catching COVID-19.

6. Take your allergy medicine

If you have seasonal allergies, the best time to take allergy meds is before your symptoms strike. It’s more effective to prevent symptoms in the first place than to stop them once they’re in full swing. Remember, keeping your symptoms under control may reduce your risk of developing a sinus infection or a weakened immune system.

Other tips to stay healthy during seasonal changes, per the Cleveland Clinic:

• Get your flu and COVID-19 vaccines (you can get them at the same time to save you an extra trip)
• Always get your annual physical
• Get plenty of sleep
• Stay hydrated

—medically reviewed by Jennifer Logan, MD, MPH