Many believe running in the rain leads directly to illness, often preventing runners from heading out in wet weather. The idea that cold or damp conditions cause a cold or the flu is a long-standing myth. Rain itself is not a pathogen and cannot directly cause an infection. However, the physiological response to getting cold and wet can temporarily shift your body’s defenses, creating a window of vulnerability related to a drop in temperature.
Viruses, Not Weather, Cause Illness
The common cold and influenza are caused by viruses, primarily rhinoviruses and the influenza virus. These illnesses require exposure to an infectious agent, typically transmitted through respiratory droplets or contaminated surfaces. Rain or cold air does not spontaneously generate these viruses within your body.
The risk of virus transmission is often higher indoors where people are crowded together in poorly ventilated spaces. Running outside in the rain generally means you are physically distanced from others, diluting any potential airborne viral load. Therefore, running in the rain, on its own, is not the mechanism that makes you sick.
How Cold Exposure Affects Immune Response
While rain does not carry pathogens, getting soaked leads to rapid heat loss through convection, quickly dropping your skin and core temperature. The body responds by initiating peripheral vasoconstriction, narrowing blood vessels near the skin and extremities. This shunts warm blood toward the internal organs, preserving core body temperature.
This protective mechanism can reduce the delivery of immune cells, such as white blood cells, to the upper respiratory tract’s mucous membranes. Cooling the nasal passages temporarily impairs localized immune defenses. Studies show that a temperature decrease of just a few degrees inside the nose can suppress the release of extracellular vesicles, which help trap and neutralize viruses.
A drop in temperature also slows the movement of cilia, the hair-like structures lining the respiratory tract. Cilia are responsible for sweeping mucus and trapped pathogens out of the airways. This temporary impairment of the mucociliary clearance system creates a brief window where an already present virus may establish an infection more easily. The risk of illness is caused by the body’s reaction to prolonged wet and cold exposure, not the rain itself.
Strategies for Safe Running in Wet Conditions
Mitigating the risk associated with running in the rain focuses on minimizing heat loss and quickly restoring normal body temperature. Layering clothing is the most effective strategy. Use materials that wick moisture away from the skin, such as synthetic fabrics or wool, rather than cotton, which retains water. The outermost layer should be wind- and water-resistant to shield your body from cooling effects.
Protecting your head, hands, and feet is also important, as extremities are prone to rapid temperature drops. A warm hat and gloves, even lightweight ones, significantly help with overall heat retention. After a rainy run, change out of all wet clothing immediately, as standing in damp garments continues the cooling process.
Taking a warm shower and consuming a warm drink post-run helps stabilize and restore your core body temperature efficiently. These immediate actions close the temporary window of vulnerability created by the physiological responses to the cold and wet.