Does Cold Weather Make You Sick? The Folk Belief Is Partly Right

Short answer: does cold weather make you sick on its own? No. Colds come from viruses, and the CDC counts more than 200 respiratory viruses that cause them. But cold is not neutral either. In a randomized trial, 13 of 90 people whose feet were chilled reported a cold afterward against 5 of 90 controls. In human nasal tissue, cooling cut the release of antiviral decoy particles by nearly 42%. Cold weather does not create the infection. It improves the odds for one.

The question in the search box is a yes-or-no question, and the honest answer is a split one. The folk belief gets the cause wrong and the association right. That makes it unusually interesting, because the research now exists to say which parts of grandmother's advice survived.

What definitely causes a cold

A cold is an infection. According to the CDC, more than 200 respiratory viruses can cause one, rhinoviruses most often in the United States, with human coronaviruses, parainfluenza viruses, adenoviruses, enteroviruses and human metapneumovirus also on the list. Influenza, RSV and SARS-CoV-2 cause cold-like symptoms, the agency notes, but are not counted as colds and are more likely to cause severe illness.

Transmission is person to person. Most respiratory viruses spread through droplets an infected person releases when they cough or sneeze, and some also through close personal contact. Adults in the US average two to three colds a year, children more, and symptoms usually peak within two to three days and clear in under a week.

Nothing in that list is weather. A person alone in a cold room with no virus present does not develop a cold. Everything below is about probability, not cause.

Belief versus what the research found

Does cold weather make you sick by chilling the body?

This is the oldest version of the question, and the one with a human trial behind it.

Johnson and Eccles, working at the Common Cold Centre in Cardiff, randomized 180 healthy subjects to either a foot-chilling procedure or a control procedure, then had them score cold symptoms before, immediately after, and twice a day for four or five days. Three results matter.

First, chilling produced no immediate symptoms: there was no acute change in symptom score (P = 0.62). Whatever happens, it is not instant.

Second, over the following days, 13 of the 90 chilled subjects reported that they had developed a cold, against 5 of the 90 controls (P = 0.047). Mean total symptom scores for days one to four were 5.16 (SD ±5.63, n = 87) in the chilled group and 2.89 (SD ±3.39, n = 88) in controls (P = 0.013). The authors' own summary is that acute chilling of the feet caused the onset of cold symptoms in about 10% of subjects.

Third, the people who went on to develop a cold (n = 18) reported significantly more colds per year than those who did not (n = 162; P = 0.007). The susceptible were already susceptible.

Two cautions. The outcome was self-reported symptoms, not a laboratory-confirmed infection, and the authors explicitly call for more work on how symptom generation relates to respiratory infection. The paper's own background notes that earlier clinical research, in which volunteers were deliberately exposed to cold viruses, found no link between cold exposure and becoming infected. So the most defensible reading is narrow: chilling appears to tip some people from carrying a virus quietly into feeling ill, in roughly one in ten. It is not evidence that cold conjures a virus from nowhere.

Most rhinovirus strains replicate better at the cooler temperatures found in the nasal cavity than at lung temperature. Foxman et al., PNAS, 2015

The nose is the cold part

The mechanistic work has converged on one piece of anatomy. The nasal cavity sits at about 33 °C, several degrees below core temperature, and it gets colder in cold air. Two studies asked what that does.

Foxman et al. (2015), mouse cells. Working with a mouse-adapted rhinovirus produced by 27 serial passages, the team compared replication at 33 °C and 37 °C. In a mouse airway cell line the virus amplified roughly 10,000-fold at 33 °C but less than 50-fold at 37 °C. In primary mouse airway cells, final titers differed about 100-fold between the two temperatures.

The explanation was not simply that the virus likes the cold. Most of the gap was the host response. In cells lacking MAVS, a signaling protein needed for the interferon response, the 33-versus-37 gap shrank to about 5-fold; in cells lacking the type I interferon receptor, to about 9-fold. Warm cells detected the virus and mounted a stronger interferon response; cool cells did less of this. The enzyme activity of the sensor RIG-I was about 65% higher at 37 °C than at 33 °C.

The limitation is important and the authors state it: these were mouse cells and a mouse-adapted virus. Human airway cells still needed to be studied. Treat this as a mechanism demonstrated in cell culture, not a measured human effect.

Huang et al. (2023), human tissue and volunteers. The Mass Eye and Ear and Northeastern group looked at extracellular vesicles, small particles the nasal lining releases into mucus, which can act as decoys that bind viruses before they reach cells. Samples came from surgical patients and healthy volunteers, and were tested against one coronavirus and two rhinoviruses that cause colds.

To find out how much a nose actually cools, four volunteers moved from a room at about 74 °F to 39.9 °F for 15 minutes. Nasal temperature fell by about 9 °F. Applying that same drop to nasal tissue in the laboratory reduced extracellular vesicle secretion by nearly 42%, and the antiviral proteins carried by those vesicles were impaired as well.

That is the single most direct answer to "can you get sick from being cold". A quarter of an hour in near-freezing air measurably cools the tissue where colds start, and a measurable part of that tissue's defense drops with it. It is still a tissue-level result rather than a count of illnesses, from four volunteers' temperature readings, and the numbers here come from the institution's write-up and contemporaneous press coverage rather than the full paper, which this article could not open.

Dry air, not just cold air

Winter air holds very little water, and indoor heating makes it drier still. Three studies suggest this is at least as important as temperature.

Shaman and Kohn (2009) reanalyzed earlier guinea pig experiments using absolute humidity, the actual water vapor content of air, in place of relative humidity. Absolute humidity explained about 50% of the variability in influenza transmission against 12% for relative humidity, and about 90% of the variability in virus survival against 36%. Both outdoor and indoor absolute humidity bottom out in winter, which the authors proposed as a physically sounder explanation of the winter peak than relative humidity. It is a reanalysis of animal data plus climate data, not a human trial.

Lowen et al. (2007) ran the underlying experiments: 20 transmission experiments in guinea pigs across combinations of temperature and humidity. At 20 °C, three or four of four exposed animals became infected at 20% and 35% relative humidity, one of four at 50%, three of four at 65%, and none of four at 80%. At 5 °C, transmission ran 75 to 100% at 35% and 50% humidity. At 30 °C and 35% humidity, no transmission was detected at all. Infected animals kept at 5 °C shed virus at peak levels for 3.93 ± 0.63 days against 2.21 ± 0.61 days at 20 °C (P < 0.0005), about 40 hours longer. Notably, upper-airway innate immune responses were similar at 5 °C and 20 °C, so in this model the cold was not suppressing the host.

Kudo et al. (2019) tested the host side directly, housing mice at 10 to 20% relative humidity or 50%, both at 20 °C, for four to seven days before influenza challenge. Mice in dry air lost weight faster, dropped in body temperature and survived less often (n = 10 per group, P < 0.05). Dry air impaired three separate things: mucociliary clearance, the escalator of mucus that carries particles out of the airway, which was significantly reduced at 10% humidity (P < 0.0001); repair of the airway lining, with far fewer proliferating epithelial cells on day six (P < 0.01); and interferon-stimulated gene induction, which rose after infection at 50% humidity but not at 10%. Viral loads were similar early on, so the difference was mostly in how the animal handled the infection rather than how much virus it carried.

All three are animal or reanalysis studies. They are the strongest available evidence on indoor winter air, which is why the practical lever most people have is the humidity level in the house in winter rather than the thermostat. For the same reason, winter advice about air purifiers addresses particles rather than humidity, and the two are not substitutes.

Mechanisms, ranked by evidence

Two patterns are worth noticing. The human evidence is thin and local: one modest trial on symptoms, one tissue study on defense. The strong quantitative effects all come from animals or from reanalysis. The indoor-crowding explanation that most articles list first is the one with no measurement behind it here.

What cold weather genuinely does cause

Shifting the odds on a cold is the weakest thing cold does to a body. The direct harms are not in dispute.

The CDC names four groups most at risk of hypothermia: older adults without adequate food, clothing or heating; babies sleeping in cold bedrooms; people who stay outdoors for long periods; and people who drink alcohol or use illicit drugs. NIOSH adds that in regions unaccustomed to winter weather, near-freezing temperatures already count as cold stress.

This is the part of the folk belief that needs no hedging. Cold does not reliably give you a cold, and it absolutely can take your fingertips.

Why winter feels like the sick season

Part of the answer is that the viruses really are seasonal. The CDC says flu activity in the US usually occurs in fall and winter and most often peaks between December and February; across the seasons from 1982–83 to 2023–24, activity peaked in February in 17 seasons, December in 7, January in 6 and March in 6. The 2020–21 season had no discernible peak. Colds, by contrast, happen year round: the CDC notes that other viruses causing cold symptoms circulate in spring, summer and fall.

Part of it is bookkeeping. Two or three colds a year, bunched into the months when flu and RSV are also circulating, produce a run of illness that feels like a pattern. And part of winter malaise is not infection at all: short days and a disrupted schedule affect sleep and mood, which is a separate question from whether you are getting enough deep sleep and from why you feel flattened after a working day.

What follows in practice

Nothing here supports buying anything, and none of it is treatment advice. What it does support is a short list of priorities.

Treat exposure as the main variable. Colds come from people, through droplets and close contact. Hand hygiene and distance from someone who is actively coughing do more than a warmer coat.

Keep the nose warm, not just the body. This is the one new thing the research adds to the old advice. Nasal tissue cools fast and its local defenses drop measurably when it does. A scarf pulled over the nose is a cheap intervention with a plausible mechanism and no measured effect size in people. Treat it as sensible, not as proven.

Dress for wet as well as cold. The hypothermia guidance is specific: being chilled by rain, sweat or immersion matters above 40 °F. Wet clothing is the common factor in the trial result, the folk belief about rain, and the CDC's warning.

Pay attention to indoor air in winter. Dry air is where the animal evidence is strongest, and it is the variable a household can actually change.

Keep cold exposure and cold weather separate. Deliberate cold exposure, from a cold shower to a plunge, is a different subject with a different literature, closer to a deliberate nervous system reset than to infection risk. The studies above say nothing about whether it helps or harms.

Questions people ask

Can you get sick from being cold? Not directly: a cold needs one of more than 200 respiratory viruses. But in a randomized trial of 180 people, 13 of 90 whose feet were chilled reported developing a cold within four or five days against 5 of 90 controls. The most careful reading is that chilling tipped some already-exposed people into symptoms.

Can you catch a cold from being cold? No. Catching a cold means acquiring a virus from another person, through droplets or close contact, and cold air contains none. What cold appears to change is how well the nose resists a virus that is already present, and how long an infectious person sheds virus into the air around them.

Does going out with wet hair make you sick? No study opened for this article tested wet hair. The closest evidence is the foot-chilling trial, in which cold water on a body surface was followed by more reported colds. Wet skin or hair in cold air cools the body faster, which is also why the CDC warns that hypothermia can happen above 40 °F when someone is wet.

Can you get sick from being wet and cold? The combination is what the hypothermia guidance singles out: chilling from rain, sweat or cold water can cause hypothermia even at temperatures above 40 °F. For colds specifically, the only human trial used cold water on the feet and found more reported colds afterward in about 10% of those chilled.

Can you get sick from being cold at night? Nothing opened here measured overnight room temperature and illness. The CDC does list babies sleeping in cold bedrooms among the groups most at risk of hypothermia, which is a different and more serious concern than a cold. A cold bedroom with no virus in it does not cause an infection.

Can you get sick from cold air blowing on you? Not by itself. Cold air blowing on the face does cool nasal tissue, and in human nasal tissue a cooling of about 9 °F cut antiviral vesicle release by nearly 42%. For people with asthma, the NHLBI lists very cold air as a trigger, which is a separate mechanism from infection.

Does cold weather weaken your immune system? The research points to local effects rather than a weakened system overall. Nasal tissue releases fewer antiviral decoy particles when cooled, and in mouse airway cells the interferon response was weaker at 33 °C than at 37 °C. In guinea pigs, upper-airway innate responses were similar at 5 °C and 20 °C.

Why do I always get sick in winter? Flu is genuinely seasonal: across 1982–83 to 2023–24 US flu activity peaked in February in 17 seasons and in December in 7. Dry winter air also helps influenza survive and spread, and impaired clearance and interferon responses in dry air in mice. Adults average two to three colds a year, and those tend to cluster in the same months.

Is dry air or cold air the bigger problem? Dry air has the larger measured effect, though only in animal and reanalysis studies. Absolute humidity explained about 50% of the variability in influenza transmission and 90% of virus survival, against 12% and 36% for relative humidity. Indoor heating is what makes winter air dry, so the two travel together.

Does being cold make an existing cold worse? No study opened here measured that. Chilling in the Cardiff trial produced no immediate change in symptom scores (P = 0.62), and higher scores appeared only over the following days. For asthma and other airway conditions, very cold air is a recognized trigger, which is a different issue from a cold's duration.

This article summarizes research on cold weather and respiratory infection for general information and is not medical advice. Much of the evidence comes from animal and cell studies, which may not transfer to people. For symptoms that worry you, for asthma or another lung condition, or for suspected hypothermia or frostbite, consult a clinician.