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Climate is not my priority because I prefer to develop the culture and the languages. However, climate has a strong influence in the culture, so I need to know the basics.

So, I have a country located between the equator and the 20° parallel. According to what I have been reading on internet, that means that it's a desert. However, in this country there's a huge mountain range and I don't know how this affects its climate.

I suppose that the mountain will be cold, but I don't know how cold and how does snow "work" in this case.

The following map (generated with this) represents the part of the world I'm interested in:

map

I'm interested in the red circle, but specially in the red dot which will most probably be the capital city of the country.

Assume an Earth-like planet (and please don't mind the river physics, I still have to edit things).

If you need me to give more details, just ask.

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    $\begingroup$ That's a strange spot for a city. For most of human history cities have been built close to water. $\endgroup$ – sphennings May 22 '17 at 14:22
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    $\begingroup$ @sphennings I know, but it has a reason. Summarizing, Verishi (the country) is a theocracy and this place is a sanctuary (because its where the first Laran Noma (aka. this religion Dalai Lama)) died. At first it was only a sanctuary, but since the religion is very important in this society, it evolved to a city. And, since the country is a theocracy ruled by the Laran Noma, the city turned to be the capital. $\endgroup$ – NeoMahler May 22 '17 at 14:28
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    $\begingroup$ I suspect this is too close to the equator to be a desert. See horse latitudes on Wikipedia. tl;dr: Sinking air between 30 and 38 degrees prevents clouds from forming. $\endgroup$ – JollyJoker May 22 '17 at 14:54
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    $\begingroup$ Also, you could have glaciers up high with rivers running from them to get your city water. $\endgroup$ – JollyJoker May 22 '17 at 15:03
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    $\begingroup$ @Michael he did that in the text too. I see that sometimes…I suppose if your language’s keyboard has that on it, it’s handy to adapt it to near lookalike uses. Hey, the following comment uses a hyphin instead of a negative symbol! - vs −. $\endgroup$ – JDługosz May 23 '17 at 7:13
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Mount Kilimanjaro is just about on the equator, and yet is snow-covered. That's because temperature drops as altitude increases.

Also, "located between the equator and the 20° parallel. According to what I have been reading on internet, that means that it's a desert" is spectacularly wrong: the Amazon rainforest is also near the equator, but is as far from "desert" as you can get. EDIT: Vietnam, Papua New Guniea, Burma, Thailand, the Philippines, etc, etc are also around the equator.

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    $\begingroup$ you could say "deserts often occur between 20 and 30 degree latitude". But the statement is really spectacularly wrong. $\endgroup$ – Fl.pf. May 22 '17 at 14:11
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    $\begingroup$ 4000 meters isn't that high and if sufficient surrounding area is at high elevation too it might not be that cold up there. $\endgroup$ – Hyfnae May 22 '17 at 14:22
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    $\begingroup$ Good distinction, desert only means dry, not necessarily hot. $\endgroup$ – Joe Kissling May 22 '17 at 14:27
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    $\begingroup$ Eh.. Burma is at the same latitude as the Sahara desert and Thailand and Vietnam aren't at the equator either. Make that: Malaysia, Singapore, Papua New Guinea, Indonesia, etc. $\endgroup$ – Erwin Bolwidt May 22 '17 at 15:27
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    $\begingroup$ Re: Joe's comment: the driest place in the world (i.e. a desert) is actually in Antarctica. The valleys are protected from two sides by steep walls and a strong, dry wind blows along them, so the place hasn't seen precipitation in millions of years. The Atacama Desert is typically said to be the driest place, but there's always a niggling "non-polar" qualifier attached. $\endgroup$ – Draco18s May 22 '17 at 18:11
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'Mountains' effect on climate is that they block moisture from passing over them (or severely limit it.)

You can see this quite clearly in the USA as shown here: precipitation map of Washington state:

Everything that has a mountain between it and the ocean is super dry and the area right in front of the mountain is super wet. That's what mountains do to climate.

However, your island/continent is not like Washington. You have ocean on four sides like this:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~water~~~~__land_______^^Mountain^^___land______~~~water~~~~~
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~~~~~~~~~~_____________^^^^^^^^^^^^_____________~~~~~~~~~~~~~ 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So you have several options. A lot depends here - where are the ocean currents and prevailing winds coming from?

  • from the north = both land areas should be wet or normal
  • from the east = the eastern lands will be wet and the western lands will be dry
  • from the south = both land areas should be wet or normal
  • from the west = the western lands will be wet and the eastern lands will be dry
  • the prevailing ocean currents and winds are dry = everywhere is dry

When using this information, please note that ocean currents can change cyclically - google El Nino for a real-life example. This means that it's possible that the area that's normally wet can sometimes be dry and vice-versa.

Now let's talk temperature. According to this reasonable-seeming website, you drop 4 degrees Fahrenhiet for every 1,000 feet, which means that mountains that are ~14,000 feet or higher are probably snow-covered year-round. Bonus points: If you go to their link, they've got a cool little graphic showing different vegetation groups for various altitudes.

Tl;Dr - because your mountain only will block East-west winds, you can freely choose what climate both sides will have, and any mountain over ~13,500 feet can expect to have snow. Also, this can be something that changes cyclically over time.

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  • $\begingroup$ Re "Everything that has a mountain between it and the ocean is super dry...": Not entirely, it depends on the prevailing winds. For instance the Atacama desert in Chile/Peru is very dry between the Pacific & the Andes, much wetter on the other side of the mountains. $\endgroup$ – jamesqf May 22 '17 at 17:17
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    $\begingroup$ @jamesqf did you read the following two paragraphs and the description of what would happen based on prevailing ocean currents and winds? $\endgroup$ – Jeutnarg May 22 '17 at 17:23
  • $\begingroup$ I probably will make the currents come from the east, so the capital city is "normal" but the other half is desert... it's more interesting that way. I will have to see how this affects other nearby countries, though. Thanks for your help! $\endgroup$ – NeoMahler May 22 '17 at 18:44
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    $\begingroup$ The presence of a major river to the east of the mountains (one of only two rivers big enough to show on the map) implies the prevailing winds are from the east (or, more likely, the northeast), causing the east side of the mountain range to be wet (think: Amazon rainforest wet) and the west side to be dry. $\endgroup$ – Mark May 22 '17 at 20:54
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That says 9000m, that's a little taller than Everest. Earth only has 14 mountains higher than 8000m, and more than half of them are in Nepal.

That mountain will be deadly cold, all year long. The air will be so thin normal people will suffocate. It will hardly ever snow because any moist air that approaches the mountain will tend to drop its moisture before it reaches the top. The mountain will still be covered in a thick layer of snow and many glaciers because the little snow that does fall there never melts.

4000m (where your city is) is still very high. The list of cities above that altitude is short. It's high enough that some visitors from the coast will sick, and they will get winded easily. You can expect harsh winters and short growing seasons. In particular, I would direct you to Cerro de Pasco in Peru, it is the located at 10 degrees south of the equator and is the highest city of that size. The wikipedia page conveniently has a simple summary of the city's climate.

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I am now going to link you to Palm Springs, CA. A town that features both 100°F daytime temperatures (yes, even during the winter, although typically a more comfortable 70–80) and is classed as a hot desert climate. Nights can get pretty cold, though, which is typical for a dry desert.

Twelve minutes away, up a tram into the adjoining mountains, with nearly 6000 feet of additional elevation, you'll find snow during the day. Or at least, temperatures 40 degrees cooler than down at the bottom (bring a jacket). Snow only falls during the winter as the mountains do get warm enough during the summer for it to melt, but the temperature gradient is staggering and as such has become quite the tourist hot-spot.

So no, a mountain in a desert is not always hot and dry.

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