How does air pressure affect humidity levels?

Humidity is the amount of water vapor present in the air, and this can be significantly influenced by air pressure. When air pressure is lower, it allows the air to expand, which can increase the capacity of the air to hold moisture. Because warmer air at low pressure can hold more water vapor, it tends to foster higher humidity levels.

When air pressure decreases, such as in weather systems associated with storms, the air lifts and cools, frequently leading to increased condensation and cloud formation. This situation is conducive to higher humidity levels because the air can hold more moisture as it rises and cools.

Conversely, higher pressure systems often lead to decreased humidity. These systems are typically associated with descending air, which compresses and warms as it descends, resulting in a drop in relative humidity. Thus, lower pressure effectively promotes conditions that can lead to increased humidity, making it the correct choice in this context.