Why Does the Nose Run When It’s Cold

The nose runs in cold weather because it adjusts incoming air before it reaches the lungs. Cold air is often dry, so the nasal passages add moisture and warm the air as it moves through. When the amount of fluid becomes greater than the nose can retain, the excess moisture leaves through the nostrils.

The nose warms and humidifies incoming air

The nose helps prepare air for the respiratory system by filtering, warming, and adding moisture. As air passes through the nasal passages, the lining of the nose adds humidity while surrounding tissues help warm the air.

Cold air often contains less moisture than warm air, so the nose increases this conditioning process when temperatures are lower. This helps adjust the air before it continues through the respiratory system.

The process also works alongside other protective responses in the airways, including sneezing and other mechanisms that help remove unwanted particles from the nose and respiratory system.

Extra moisture becomes a runny nose

The moisture added inside the nasal passages normally stays along the lining of the nose. In cold conditions, the amount produced can increase beyond what the nasal passages can hold.

The extra fluid then moves forward and leaves the nose as a runny nose. This response comes from the nose adapting to cold, dry air rather than from the temperature itself creating a separate source of fluid.

Cold conditions can affect moisture movement

Cold air can also influence how moisture behaves inside the nose. The difference between cold outside air and the warmer, more humid environment inside the nasal passages can contribute to condensation.

This adds to the moisture already present, but the main cause of a runny nose in cold weather is the increased need to warm and humidify incoming air. Similar temperature-related responses can also affect other body functions, such as shivering when cold.

Putting it all in context

A runny nose in cold conditions happens because the nose adjusts the air entering the respiratory system. By warming and adding moisture to cold, dry air, the nasal passages help prepare it before it moves deeper into the airways. When excess fluid builds up, it leaves through the nostrils as part of this normal response.

Discover how physical processes work in everyday situations within the Health & Body category.