No - Mayo Clinic is direct: wet hair in a cold environment can make you uncomfortable, but it will not give you a cold; wet hair does not make you more attractive to viruses.
Colds come from viruses arriving through contact - a sick person coughing or sneezing nearby. The myth survives on correlation: cold wet months are also virus season - indoor crowding, dry air, slightly weakened nasal defense - and the hair gets blamed. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
Does wet hair outside make you sick?
No - this one the evidence settles completely. Mayo Clinic's answer is as direct as medicine gets: wet hair in a cold environment can make you feel cold and uncomfortable, but it will not give you a cold. Colds, flu, and COVID come from viruses, and viruses arrive through contact - usually someone sick coughing, sneezing, or blowing their nose near you. Wet hair does not make you more attractive to viruses and does not raise your chances of infection. The myth survives on correlation: cold, wet months are also virus season - indoor crowding, dry air, and slightly weakened nasal defenses - so people get sick in the same weather that soaks them, and the hair gets blamed. One honest footnote: research does show a chilled nose defends itself slightly worse, so the umbrella is not pointless - but it is defense against weather, not germs. The actual variables worth controlling: hand hygiene, indoor ventilation, and distance from the visibly ill. The damp head is innocent.