The island of Sanctuary is a flat disc about 200 miles in diameter. Sanctuary lies within a pocket dimension, so it has an artificial sun. The artificial sun is roughly 100 miles above the island; it turns itself on and off in a day/night cycle, and it circles above the island at a radius of about 50 miles. The ocean is connected to the Elemental Plane of Water (and the atmosphere is connected to the Elemental Plane of Air), which has a constant cooling effect on the island; the sun produces enough heat to keep the island comfortable.

What sort of weather does this lead to?

My guess is: rain happens at night, when the sun is off and the air cools. Rain does not happen during the day, because the air is warming up.

But what happens with the winds? Are there strong winds blowing away from the sun during the day and towards it at night? Is the wind and rain stronger on the edge of the island that's far from the sun, or is it stronger near the sun?

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    $\begingroup$ Only thing I can think of are rainshowers induced by convection, but that requires the temperature declining as you ascend. With a sun that close to your surface I don't think predicting weather in any common sense is possible. Basically the weather is whatever you think it should be in the circumstances you've built. $\endgroup$
    – Hyfnae
    May 21, 2017 at 20:00
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    $\begingroup$ If you have connections to Elemental Planes won't that wild card have a lot to do with the weather? For example will a wind storm in the Plane of Air cause wind in your pocket dimension? $\endgroup$
    – Willk
    May 21, 2017 at 20:04
  • $\begingroup$ @hyfnae but en.wikipedia.org/wiki/File:Thunderstorm_formation.jpg tells me that clouds don't go much higher than ten miles. The atmosphere of Earth is around 60 miles high. It seems like 100 miles should be enough. $\endgroup$
    – Dan B
    May 21, 2017 at 20:09
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    $\begingroup$ The weather probably functions at the whims of the creator of the pocket dimension. If I was going to create a pocket dimension I'd be sure that it was climate controlled. $\endgroup$
    – sphennings
    May 21, 2017 at 20:12
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    $\begingroup$ I don’t think anyone has modeled how elemental planes create weather conditions. I don’t think this can be answered with the information given. $\endgroup$
    – JDługosz
    May 22, 2017 at 6:47

1 Answer 1


The short answer is that whoever is powerful enough to set up the pocket dimension will be capable of creating whatever weather conditions they want. Which means that you as the author can decide.

That being said, we can do some guesses.

If the elemental plane of Air contains only air, with no water in it, the atmosphere will probably never contain enough water to create rain.

Sure, water will be continuously evaporating, but the wet air will be blown into the plane of Air before it gets wet enough.

However, this depends on there being enough air exchanged daily. As the creator you can set this how you want.

There is also the ocean to consider. How hot is the water in the plane of Water? Will the local sun have time to heat it significantly before it disappears back into the elemental plane? How wide is the oceans around the island? All this can be changed around as you wish.

And then there is the ground. How well does it retain heat during the night? This decides how cold it gets and how much thermal wind you will be seeing. The higher the temperature difference, the more wind. However, this will not be much of a wind. Look at Sea breeze for more info.

If you do set up things so that you get rain, it will probably fall at night, probably as a light drizzle.


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