Contrary to popular belief, going outside with wet hair probably won’t cause you to catch a cold. Though research is ongoing, most studies have shown that being exposed to cold temperatures does not increase the likelihood that someone will catch a cold. People generally catch the common cold through exposure to other infected people, usually via contact with droplets from the infected person’s sneeze.
More about the common cold:
A few studies show that cold temperatures may be associated with catching a cold because exposure to cold can suppress immunity, making people more susceptible to illness.
Experiments performed by Louis Pasteur and a study of soldiers during World War I might have contributed to the mistaken idea that cold and damp cause colds. In the first case, Pasteur exposed chickens to anthrax and then either dipped their feet in cold water or wrapped them in a warm blanket. Those wrapped in a warm blanket were more likely to survive. The study of World War I veterans showed that those who slept in damp trenches were more likely to die than those sleeping in barracks.
One explanation for why people seem to get more colds and flu in the winter is that people are more likely to stay indoors during the colder months, bringing them into more frequent and close contact with people who are contagious.
Although they are often confused with each other, the common cold and influenza are two separate conditions. Flu symptoms are often more severe than cold symptoms, and their onset is more quick and strong. People who have the flu often develop fevers, which is relatively rare among cold sufferers.