Humid Green &
An area is designated "humid" when the rainfall exceeds the rate of evaporation.
And, well, "dry" is dry.
On islands with alternate wet and dry seasons, such as the Virgin Islands, the trees shed their leaves in the dry season and resemble a bare winter scene.
But when the water turns back on, everything is green again. This alternating pattern of grimness and greenness, which makes up a great deal of the Caribbean, is referred to as dry and green humid forests.
In the driest regions where little rain falls at anytime during the year, dry scrub vegetation is the major characteristic. The arid islands of Aruba , Bonaire and Curacao fit this category perfectly.
Rainfall there is so scarce that most of the water for human consumption is supplied from seawater through desalinization plants.
The cactus in these dry regions come in many different varieties and shapes may be small or 20-30 feet high. Agaves, spiny opuntias and thorny shrubs are also characteristic of this kind of rugged, tough terrain.
Hiking is such areas calls for extra water and very good shoes, since the spines of some cactus can deeply penetrate shoe soles.
Depending on how high the mountains and the wind direction, it's possible to have both humid and arid regions on the same island.