“Cold weather makes you sick.”

• Cold temperatures directly cause genuine illness and injury independent of any pathogen: hypothermia, frostbite, and chilblains are diagnoses caused purely by cold exposure.
• Cold exposure raises blood pressure, increases blood viscosity and constricts coronary arteries, and is associated with measurable increases in heart attacks and strokes during cold snaps — a direct physiological 'cold makes you sick' pathway.
• Laboratory work shows human rhinovirus replicates more efficiently and the innate antiviral (interferon) response of airway cells is weaker at cooler temperatures (~33°C, typical of a chilled nasal passage) than at core body temperature (37°C), providing a mechanism by which chilling the nose increases susceptibility to infection.
• Research published in the Journal of Allergy and Clinical Immunology (2022) reported that dropping nasal temperature by a few degrees sharply reduced the nose's extracellular-vesicle antiviral defenses, supporting the idea that cold air blunts front-line immunity.
• Guinea pig transmission experiments (Lowen et al., PLoS Pathogens 2007) showed influenza transmits far more efficiently at low temperature and low humidity, one explanation for the winter seasonality of respiratory infections.
• Population data show excess winter mortality and clear winter peaks in influenza, RSV and common colds in temperate countries, so 'cold weather season' and 'getting sick' are strongly correlated in practice.

• As literally worded, the claim confuses correlation with cause: colds and flu are caused by viruses. Without exposure to a pathogen, cold weather alone cannot give you a cold, flu or COVID, no matter how long you stay outside underdressed.
• Classic experimental studies in which volunteers were chilled, soaked, or exposed to cold air but not inoculated with virus failed to produce colds; those given virus got sick at similar rates whether chilled or not, which is why NHS, Mayo Clinic, CDC and MedlinePlus all describe 'going out in the cold gives you a cold' as a myth.
• Winter illness peaks are substantially explained by confounders other than temperature itself: more time spent indoors in close contact, poorer ventilation, low absolute humidity favouring virus survival, school terms, and reduced sunlight/vitamin D.
• Some of the coldest inhabited places have low respiratory illness rates in deep winter when people are isolated, while tropical regions have year-round influenza — inconsistent with temperature being the direct cause.
• The cold-nose and cold-foot findings show increased *susceptibility* to an already-present virus, not disease causation; the effect size in humans is modest and some trials (e.g., Eccles's cold-feet studies) are small and contested.
• The statement's unqualified wording ('makes you sick') supports a widespread folk belief that leads people to blame weather rather than contagion — the framing fact-checkers and health agencies specifically warn against.

85/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Proceedings of the National Academy of Sciences (Foxman et al., 2015)journal · 95 · PLoS Pathogens (Lowen et al., 2007)journal · 93 · UK National Health Servicegov · 93 · Mayo Clinicedu · 90 · MedlinePlus, U.S. National Library of Medicinegov · 92 · U.S. Centers for Disease Control and Preventiongov · 93 · Johns Hopkins Medicineedu · 90

• Cold weather can indirectly raise the risk of respiratory infections: laboratory and epidemiological literature finds that lower temperatures and low humidity can favor respiratory-virus survival/transmission and that people tend to spend more time indoors in close contact during colder seasons.
• Experimental evidence suggests colder nasal-airway temperatures can weaken local antiviral defenses. A Journal of Allergy and Clinical Immunology study found cold exposure impaired extracellular-vesicle-mediated nasal antiviral immunity, and a PNAS study found cooler airway-cell temperatures reduced innate antiviral defenses against rhinovirus.
• Cold weather can directly cause some illnesses or injuries, such as hypothermia and frostbite, so the statement is not wholly false if 'sick' is used broadly rather than specifically to mean colds/flu.

• Cold weather by itself does not cause the common cold, flu, COVID-19, or other viral respiratory infections; infectious viruses or other pathogens are required. CDC describes common colds as being caused by viruses, especially rhinoviruses.
• MedlinePlus explicitly states that, contrary to popular belief, cold weather or becoming chilled does not cause a cold, though colds are more common in colder seasons.
• The claim as written omits the key distinction between a risk factor and a cause. Cold conditions may increase susceptibility or transmission under some circumstances, but they do not 'make you sick' in the infectious-disease sense without exposure to a pathogen.

87/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Centers for Disease Control and Preventiongov · 96 · MedlinePlus / U.S. National Library of Medicinegov · 94 · Journal of Allergy and Clinical Immunologyjournal · 92 · Proceedings of the National Academy of Sciencesjournal · 91 · Annual Review of Virologyjournal · 90

• Cold weather changes human behavior by driving people indoors, where poorer ventilation and close proximity to others significantly increase the transmission rate of viruses.
• Many respiratory pathogens, such as rhinoviruses (which cause the common cold) and influenza, survive longer and replicate more efficiently in colder, drier air.
• A 2022 study published in The Journal of Allergy and Clinical Immunology demonstrated that inhaling cold air significantly lowers the temperature inside the nasal cavity, which suppresses the local immune response (specifically, the release of virus-fighting extracellular vesicles), making infection more likely if a virus is present.
• Extreme cold can directly cause non-infectious environmental illnesses like hypothermia and frostbite, and cold, dry air can trigger asthma attacks or exacerbate cardiovascular issues.

• Infectious diseases like the common cold and the flu are caused by exposure to pathogens (viruses and bacteria), not by low temperatures or weather.
• Without the presence of a specific virus, a person cannot catch a cold or the flu simply by being outside in freezing weather, regardless of whether they have wet hair or lack a coat.
• Medical consensus and major health organizations consistently categorize the direct causal claim that 'being cold gives you a cold' as a persistent myth and old wives' tale.

98/100 — the lab’s own confidence in the score above, not a second reading of the claim.

National Institutes of Health (NIH)gov · 95 · The Journal of Allergy and Clinical Immunologyjournal · 90 · American Heart Associationedu · 90

• Cold weather does not create a cold or influenza infection by itself; however, lower temperature and humidity can increase the occurrence and transmission of several respiratory viruses. A peer-reviewed study found that decreases in temperature and absolute humidity were associated with increased human rhinovirus infections, although risk was lower at subfreezing temperatures.[https://pmc.ncbi.nlm.nih.gov/articles/PMC5035958/]
• A review in a scientific journal reports that low temperature and humidity can increase respiratory-virus stability and transmissibility, promote indoor transmission, and reduce some host immune responses.[https://pmc.ncbi.nlm.nih.gov/articles/PMC8988196/]
• A review of environmental and viral-infection research reports that cold temperatures are believed to increase transmission of respiratory viruses including RSV and rhinovirus.[https://pmc.ncbi.nlm.nih.gov/articles/PMC7395586/]
• Cold exposure itself can cause noninfectious health problems, including hypothermia and frostbite, so cold weather can directly make a person ill even without an infection.

• The CDC states that common colds are caused by more than 200 respiratory viruses, with rhinoviruses the most frequent cause; this means the infectious cause is a virus, not cold weather itself.[https://www.cdc.gov/common-cold/about/index.html]
• The CDC states that people can get a cold at any time of year, while some respiratory viruses circulate more commonly in winter. This undermines the literal claim that cold weather itself makes people sick.[https://www.cdc.gov/common-cold/about/index.html]
• The relationship is not universal across viruses or temperatures: one peer-reviewed seasonal survey found low temperature associated with several respiratory viruses but found no association with rhinovirus incidence, and the rhinovirus study found lower risk at subfreezing temperatures.[https://pmc.ncbi.nlm.nih.gov/articles/PMC7106483/][https://pmc.ncbi.nlm.nih.gov/articles/PMC5035958/]
• Illness during cold weather can also reflect behavioral and environmental factors, such as increased time indoors and closer contact among people, rather than outdoor cold acting as a direct infectious cause.[https://pmc.ncbi.nlm.nih.gov/articles/PMC8988196/]

91/100 — the lab’s own confidence in the score above, not a second reading of the claim.

U.S. Centers for Disease Control and Preventiongov · 98 · Peer-reviewed study indexed by PubMed Centraljournal · 90 · Peer-reviewed review indexed by PubMed Centraljournal · 91 · Peer-reviewed review indexed by PubMed Centraljournal · 88 · Peer-reviewed epidemiological study indexed by PubMed Centraljournal · 87

• Respiratory viruses (influenza, rhinoviruses) survive longer and transmit more readily in cold, dry air typical of winter.
• People spend more time indoors in close contact during cold weather, raising transmission rates.
• A 2022 study found cooler nasal temperatures impair local antiviral immune defenses (extracellular vesicle response), making infection easier after exposure.
• Epidemiology consistently shows peaks of colds and flu in winter months in temperate climates.

• Colds, flu, and similar illnesses are caused by viruses (or sometimes bacteria), not by low temperature itself; infection requires exposure to the pathogen.
• People routinely spend time in cold weather without becoming ill, and these infections occur (at lower rates) in warm seasons as well.
• Classic controlled studies found that chilling volunteers did not reliably increase cold incidence in the absence of virus exposure.
• The claim as written treats temperature as a direct cause rather than a contributing environmental factor.

82/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Mayo Clinicother · 90 · Journal of Allergy and Clinical Immunologyjournal · 88