Final answer:
In cold weather, when condensate overwhelms the ability of mucus to reabsorb water, mucus buildup occurs. This is due to the air's reduced ability to hold moisture, resulting in an overproduction of mucus.
Step-by-step explanation:
In cold weather, the formation of condensates exceeding the ability of mucus to reabsorb water leads to mucus buildup. As the air gets colder, water vapor in the air can condense, much like how condensation forms on the outside of a cold beverage glass (a) or in the form of fog (b). When the water condenses faster than it can be reabsorbed by the mucus in the respiratory tracts, it can lead to an accumulation of mucus. This is because cold air can hold less moisture, and the body responds by producing more mucus to warm and humidify the air before it reaches the lungs. However, with excess condensation, the mucus may become thicker and more plentiful, potentially leading to discomfort or respiratory issues.