Why is your body cold if you stand outside in your underwear?

Your body feels cold when standing outside in your underwear because you lose heat rapidly through convection, conduction, and radiation. The lack of adequate clothing exposes your skin directly to the colder air, which draws heat away from your body more efficiently. Additionally, moisture from sweat or humidity can increase heat loss further, making you feel even colder. This combination of factors can lead to a significant drop in body temperature.