I have created a map of an island and was wondering if it is possible for a forest with a similar climate to that of a jungle to have a rain cloud above it 24/7 on this island?


On my island there is a volcano that has recently gone off so yes their is volcanic ash in the air. The forever raining forest is on the edge of the island between two mountains.

  • $\begingroup$ Related question: worldbuilding.stackexchange.com/questions/14300/… $\endgroup$
    – kuhl
    Jul 4, 2016 at 14:09
  • $\begingroup$ When I get home I'll see if I can try for a factual answer. I used to live in a city where I experienced some really long rains (lasting over 20 hours), so that could be a base for what you want. $\endgroup$ Jul 4, 2016 at 16:25

4 Answers 4


It would be nice to have some more details (Sun? Atmosphere?) but on the most fundamental level:

Clouds form when water vapor in the atmosphere condenses into droplets (can be either ice or water, or a combination of the two). The condensation point is a combination of both the temperature of the atmosphere and the amount of water vapor within the atmosphere (look up the Clausius-Clapeyron relationship to see the connection between temperature and the saturation point). On Earth, the tropical latitudes are much more humid due to evaporation of ocean water/evapotranspiration, but warmer air also has a greater capacity to retain moisture without condensation.

It gets more complicated when you factor in things like atmospheric circulation or topography. In areas with low surface pressure, air converges on that location and rises. As it rises, it expands and cools and clouds will form. Topography does something similar when mountains force air from lower altitudes up into the higher altitudes, where it will similarly expand and cool.

So to answer your question: 24/7? Probably not, unless the physics of your world are somehow different. Atmospheric circulations are mechanisms that are intended to restore pressure, energy, etc. values to equilibrium. That cloud would probably rain out at some point. Note, however, that there could be other things that would act like clouds-- volcanic ash, for one. The eruption of Mount Tambora in 1816 resulted in the Year Without a Summer


This could be possible depending on the size of the island and the type of trees in the forest.


Forests have been shown to play an important role in the formation of clouds and in the stability of rainfall. Trees suck up water from the ground in large quantities and most of that water is exhaled right out again through the leaves. Vegetation stand for as much as 90% of all moisture in the athmosphere and trees produce much more than smaller plants.

Forests also release tiny airborn particles like dust, bacteria, pollen and fungal spores into the air that promote condensation and gather the resulting moisture, hastening cloud formation

Research on deforestation shows that rainfall decreases and cloud formation lessens when trees are cut down. In similar ways rainfall can be increased through the planting of new forests.

But you're on an island, so what stopps the moisture from just drifting off due to winds?


If you could considder having mountains in a half moon shape on your island it could both help keep the local moisture put, but also contribute more moisture due to condensating moist air blown in from the sea. This would require the opening of the half moon shape to be facing the most common wind direction and that the most common wind direction blows in from a warmer area.

Then with the right conditions I think you could very well have about 24/rain with some seasonal variations. For instance, if the winds turn for a long period the cloud cover might thin out. Or if the wheather is colder the winds might bring less moisture.


Yes, it is possible if, and only if, it is big enough priority for you.

If a planet is tidally locked, mostly covered by ocean, and the numbers are right an island directly "under the sun" will be the center of a climate "cell". Surrounded by descending air currents and with a strong ascending air current on top of it. Essentially the descending air currents surrounding the island are overpowering the shadow of the permanent clouds.

A permanent column of ascending air forced by winds coming over warm ocean equals permanent rain.

And please do not ask me what the "right numbers" would be. I have no idea. The main problem is that you want a permanent rain, not a permanent "eye of the hurricane". Although your island could, of course, be ring shaped or just located with the ring of permanent rain.

The real main issue is that while you get your island of rain, you have to accept a world without nights or seasons.


Rainforest are caused - well, basically, by being on the Equator. The really huge angle of incidence of sunlight makes heating capability of the Sun the most effective on the entire planet - it means that a special air circulation takes into action: heated air raises at the equator (basic physics: hot air is less dense than cold air and thus lighter) and as it cools down in the atmosphere, water condensates and forms clouds, and then rain.

A typical cold front - you may even be witness of similar phenomena in a hot summer day!

Well, this being constant is a hard question, especially 24/7. I doubt it's possible in any area not having huge angle of incidence. For an island, though, it's not that hard.

You may consider planning out artificial weather modification effects - its origins and purposes might be hard to justify, but it's only up to you!


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