How Does Condensation Form?

Moisture in the air is controlled by the conditions it is exposed to, and cold air has a lower water content than warm air. In a basement, the amount of moisture that can be held is lower than it is outside because of the lower temperature. 

There is a limit to the amount of water the surrounding air can hold when humidity levels are high. As a result, the water in your basement has no choice except to condense into droplets that collect on various surfaces. Condensation can form in your basement very rapidly if you allow outside air or humidity in.