Up in the Air

The average level of Relative humidity in the Virgin Islands is 57% - 87%. The relative humidity is the amount of water in the air compared to how much water the air can hold. This means the Virgin Islands is a humid area.

The high levels of humidity allow the dew point to be reached much easier than in less humid climates. The dew point is when the air is fully saturated (relative humidity is 100%). It is not uncommon to see condensation in the form of morning dew or fog on the islands because the temperature drop during the night causes the amount of water the air can hold to drop which lowers the dew point.

As volcanic formed islands the Virgin Islands are mountainous. The main type of fog to form is valley fog due to the colder air draining from the tops of the mountains. Radiation fog and advection fog are the least likely types to form because it doesn’t typically get cold enough for advection fog and there is usually to much wind for radiation fog.

Another aspect affected by the dew point is clouds. As altitude increases air pressure drops allowing the dew point to drop. Clouds only form at or above the dew point. Due to the high humidity lower level clouds such as stratus (low level) and alto (middle level) tend to form.


http://weatherspark.com/averages/33722/St-Thomas-VI-US-Virgin-Islands