Scientists may finally be able to confirm the widely-held suspicion that bad weather can make you sick.

While the common cold’s name seems to imply that cold weather is responsible for the nose-running, throat-burning misery, the scientific community has been unable to establish exactly how a chill in the air might lead to the sniffles—until now. Just last week, a team of scientists from Yale University announced their discovery that lower temperatures weaken the nose’s first line of immune defenses.

The researchers started out by modifying a strain of rhinovirus—the kind of virus that causes most colds—to infect mice. (The modification was necessary because most cold viruses that infect humans don’t seem to infect rodents). They then tested how well the cells that line mouse airways fought off the virus at different temperatures, finding that cooler temperatures meant a more sluggish immune response and a greater susceptibility to infection.