Yes, it’s indeed a common misconception that cold weather directly causes illness, but science disagrees. Only pathogens—specifically viruses and bacteria—can actually cause infectious diseases like colds and the flu, which people often associate with winter. Unlike autoimmune, genetic, metabolic, or inflammatory diseases, which have diverse causes, infectious diseases spread through microbial agents, not temperature alone.
This myth is partly reinforced by language. In English, "cold" refers both to low temperatures and to the common cold, leading many to believe one causes the other. While colds and flu are indeed more prevalent in winter, this is a correlation, not causation. Studies confirm that low temperatures alone do not increase infection risk. For instance, a 1968 study published in The New England Journal of Medicine (https://www.nejm.org/doi/abs/10.1056/NEJM196810032791404) found that participants exposed to different temperatures while in contact with cold viruses showed no increased infection rates or severity or duration.
The seasonal rise in these illnesses can be explained instead by behavioral and environmental factors. In cold weather, people tend to gather indoors, in confined spaces with poor ventilation, which increases virus transmission. The News in Health article "Clearing the Air" discusses how such conditions make it easier for airborne viruses to spread (https://newsinhealth.nih.gov/2023/12/clearing-air).
Humidity also plays a significant role. Viruses remain airborne longer in dry, winter air. Low humidity prevents moisture from forming around viral particles, allowing them to stay suspended and infectious for longer periods. Conversely, during warm, humid summer months, condensation weighs viruses down, causing them to fall out of the air more quickly. Furthermore, a 2023 study published in PNAS Nexus (https://academic.oup.com/pnasnexus/article/2/2/pgac301/6960684?login=false) found that, in an environment where the air is dry, all viruses causing infectious diseases are likely to stay twice as long in the drier air, in part because they are able to use the saliva emitted with them as a protective barrier.
While wearing warm clothing can help maintain body temperature, it doesn’t prevent infections. Scarves and similar items can act as partial barriers, reducing exposure to airborne virus particles. However, prolonged exposure to cold can reduce body temperature and lead to hypothermia, as described in Health Link BC's article on Hypothermia and Cold Temperature Exposure (https://www.healthlinkbc.ca/health-topics/hypothermia-and-cold-temperature-exposure).
In short, cold weather itself does not make you sick. Instead, it’s the indirect effects—like spending more time indoors and reduced humidity—that increase the risk of illness during colder months.