This question is not a duplicate of this question. They're similar, but this one has one very large difference: only a large area has permanent cloud cover, not the whole planet.

If low clouds or even fog completely cover a large area (let's say 100 miles sq, about 161 km sq), what would be the effects on the climate? Could people still live there? (Disregard for the moment whether they would want to.)


  • Assume that light can get through, just as light does on a rainy day. The sky and sun cannot be visibly seen though.
  • Beyond where there are clouds, the climate is normal and similar to that of Earth.
  • I don't know if it matters or not, but the area directly below the clouds is a vast swamp.
  • 3
    $\begingroup$ Kudos to you for pointing to the existing question and pointing out the difference. Seeing the title, I was pretty sure we'd had a very similar question already; seeing the first sentence and the linked questions sidebar, I now at least know that you have done some searching before posting this. $\endgroup$
    – user
    Commented Mar 12, 2017 at 1:58
  • $\begingroup$ similar to a rain forest, only a swamp. $\endgroup$
    – Necessity
    Commented Mar 12, 2017 at 2:05
  • $\begingroup$ Spent much time in the Pacific Northwest? Because you're describing just a slightly more extreme version of the Pacific coast from about Monterey north to Seattle. And from what I've read, on north to Juneau. $\endgroup$
    – jamesqf
    Commented Mar 12, 2017 at 3:35
  • $\begingroup$ @jamesqf I live in Oregon. There is nothing close to permanent cloud cover here, even in the winter like it is now. There are plenty of days where it is perfectly clear. That being said: I am describing a basic rainy day (with lower clouds perhaps) that we have here, but on a permanent basis. $\endgroup$ Commented Mar 12, 2017 at 6:16
  • $\begingroup$ @Necessity Why a swamp? Could you clarify in an answer? $\endgroup$ Commented Mar 12, 2017 at 6:17

2 Answers 2


I imagine you would end up with an ecosystem akin to a cloud forest, but with a few differences. Given that the light would be constantly diffuse and scattered you would probably end up with more mosses and smaller leafy plants than you would larger trees with their larger and fairly directional leaves. Such an environment may be favorable for Carnivorous Plants due to the acidic soil if you are looking for entertaining settings.

As already mentioned, Vitamin D deficiency would be a hazard to those living in such an area due to the low amount of UV penetrating the clouds. If this area has persisted for long enough for evolution to go to work you will likely see things that cannot tolerate UV for long and have polarized vision to see better in the scattered light.

On the whole, everything would be perpetually cool and damp. I wouldn't expect there to be many large animals; but you may get a handful of apex predators and a whole bunch of prey. Plenty of things like insects and rodents.

Geologically speaking you would get methane and tar seeps from the accumulated biomass (again if the environment has persisted for a very long time). If there is some means for water to move and the correct underlying rock layers the acidic soil would create runoff that could hollow out caves.

  • $\begingroup$ Thank you for your answer; it sounds like exactly what I'm looking for. Two questions: what is polarized vision? A quick google search doesn't turn up much. And what would be the effects of methane seeps? Are we talking enough gas to ignite in the presence of a torch? Or would it escape too quickly? Is it possible that methane-dependent bacteria could start colonies around the methane seeps, similar to underwater vents? $\endgroup$ Commented Mar 13, 2017 at 6:00
  • $\begingroup$ When I say polarized vision I mean eyes with lenses that behave in a way to reduce the effects of scattered light. I doubt they currently exist in nature, but there are naturally occurring crystals that can polarize light so it's not inconceivable that evolution would find a way to incorporate them into eyes. On the methane seeps you could very easily have a situation where enough bubbles up to be lit with a torch or lightning strike, maybe eve explosively. And you would certainly get colonies of methane reducing bacteria around the seeps. $\endgroup$ Commented Mar 13, 2017 at 12:34

Well it sounds interesting and here is your answer.

If an area is permanently under cloud cover then a few things will be affected. First of all we can say about the vegetation of that area that the vegetation will get affected because we know that sunlight is vital for Plant growth. So vegetation of that area will most probably die or to some extent get reduced below an adequate level.

The second thing is that the people will suffer from vitamin D deficiency as sunlight is needed for the production of vitamin D.

Third , if the clouds are filled with water or if they are rain clouds, there might be a heavy downpour and this may cause floods and block all the communication channels which might lead to a very critical condition in regards to the communcation with the rest of the world.

The general temperature of that place will also decrease at an annual rate.

The last thing is that this place will turn into Forks, which is a city in the USA. You might have seen it in the movie twilight. 😉


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