I can hear my grandma saying, “Don’t go outside with wet hair, you’ll catch pneumonia,” right now. We’ve all been told to bundle up, close the cracked windows, and be extra careful in cold weather to avoid getting sick. And sure, colds and flu explode every winter. But is the weather actually the culprit? Not exactly.
Viruses make people sick. Cold air does not. That part is settled science. Colds come from rhinoviruses. Flu comes from influenza viruses. COVID comes from SARS-CoV-2. You can’t inhale an infection from a chilly breeze. What winter does bring is a perfect environment for viruses to spread and for bodies to struggle a little more than usual.
Start with the air itself. Cold seasons come with lower humidity, especially indoors, since heaters are running at full force. Dry air keeps virus-filled particles floating around longer after someone coughs, talks, or even breathes. Research summarized by ScienceAlert and backed by lab studies shows respiratory viruses survive longer and stay infectious in cold, dry conditions. That gives them more chances to reach another person’s nose or mouth.
Your nose also takes a hit. Breathing cold air lowers the temperature inside the nasal passages. That causes blood vessels to constrict, which reduces the flow of immune cells that normally act as bouncers at the door. Studies have shown that this cooling effect weakens the nose’s ability to stop viruses early. This gives them time to settle deeper into the respiratory tract.
In winter, human behavior also changes. People crowd indoors. Windows stay shut. Ventilation suffers. Offices, classrooms, bars, and public transit turn into shared air situations for hours at a time. That close contact gives viruses a smooth path from one host to the next, regardless of how many layers everyone is wearing.
Sunlight plays a smaller but real part too. Less daylight means less vitamin D production in the skin. Vitamin D helps regulate immune responses, and low levels have been linked to increased susceptibility to respiratory infections. Indoor heating adds another complication by drying out the mucus lining the nose and throat. That mucus normally traps viruses and moves them out. When it dries, it’s a free-for-all for viruses to enter cells.
None of this means winter equals inevitable illness. It means winter stacks the deck. Cold air helps viruses linger, limits some early immune defenses, and pushes people into conditions where infections pass easily. Wearing a coat won’t stop a virus. Fresh air, better ventilation, hand hygiene, and staying home when sick are the best bets.
Your grandma wasn’t wrong about winter being risky. She just blamed the wrong part.
The post Is Cold Weather the Reason You’re Always Sick in Winter? appeared first on VICE.
