Here is Enya with her usual silky voice, soothing and relaxing as ever. Every word, every sentence, is the result of superimposing dozens of vocals to form this peculiar soft voice as if come from heaven on the wings of a gentle breeze.

Though I walk through
warm sands in Africa
winds will grow soon
to storms in Africa.

How far to go
I cannot say.
How many more
will journey this way?

Dark skies fall on
black earth and ivory.
Far from your sun
clouds now close over me.

How far to go
I cannot say.
How many more
will journey this way?

Storms have come!
rains wash the earth away
Dark skies fall down
into another day.

Rains have now come
from storms in Africa
Time will go on
through Storms in Africa

TO STORMS= The complete sentence is "winds will grow soon to storms in Africa". If something grows to something else, it changes into that new thing:
- your hate will grow to love
- this soft music will grow to an explosion of sound by the end of the song.

CANNOT= /kænət/ The negative of CAN is CANNOT (it is not correct to spell it "can not")

JOURNEY= (formal or poetical) Travel. Though this word is usually a noun, here it is obviously used as a verb (they will journey)

BLACK EARTH AND IVORY= Ivory is a very expensive material made from elephant tusks (the two big white teeth protruding out of its mouth). Here, "ivory" refers to the elephants.
Also, "black earth" refers to the dark fertile soil of the jungle, and it is used here to refer to the jungle as a whole.
A synecdoche /sɪnekdəkɪ/ is a figure of speech in which a part is used for the whole:
- He had three mouths to feed (he had to get money for three people at home)
- The crown has nothing to say about all that sad affair (the queen/king made no declarations)
- We need all the hands available (all the people who can help)
So in this line we have thre synecdoches:
- black earth = the jungle
- ivory = elephants
- black earth and ivory = the jungle and elephants = Africa's flora and fauna = Africa.
In a way, we can say that the song began in the dry desert in northern Africa (walking in the warm sands) and after the storm, it turned into the fertile lands of black Africa, as a metaphor of the rain bringing life and fertility.

CLOUDS CLOSE OVER ME= When the clouds close, they cover the sky completely, so you can't see any blue patch. (this "close" is the oposite of "open", not the equivalent of "near")

DARK SKIES FALL DOWN= A dark sky is covered with very thick clouds, so the light of the sun can hardly go through them, that's why they look dark. These clouds usually bring a lot of rain (because they are very tall formations). If we say that the skies fall down, we mean that it rains a lot, very very much.

INTO ANOTHER DAY= The sentence is "dark skies fall down into another day". The preposition INTO means transformation, changing from something into something else, so this sentence means that the heavy rains ended and the storm changed into a new day, the stormy day was transformed into a sunny day full of new life.

This song might be a metaphor of something, like her life, a love... or simply a description of the beauty of a storm in the desert (though I walk through warm sands...).

She describes how the storm begins to grow: the skies get dark, clouds gather and finally the skies fall down... into another day.

So the rain is something that refreshes and washes, something that purifies and brings about a new beginning, a better day or simply something that releases all the tension accumulated for some time, making things fine again.

The chorus is the part that suggests that this description of nature could be a metaphor:

How far to go, I cannot say. How many more will journey this way?

She's travelling, but she doesn't know exactly where she must go, she certainly doesn't know where is the end of her journey, and she also wonders if she is the only one going that way or many more people in the future will live through the same situation as she is living now.

The metaphor could well be a love relationship, probably full of passion (warm sands in Africa). Things are going well (she's walking on "warm" sands, not "hot" sands, so it's fine), but then a storm gathers (problems, a bad time). Storm breaks out (a quarrel?), rain pours down (tension released) and finally everything's alright again (rains wash the earth away) and life goes on. But of course, storms will come again in the future, only to go away, because a relationship has its good moments and its bad moments, but we must simply accept that's the way it is (time will go on through storms in Africa).

We start in the desert and after the storm, we end up in the green jungle full of life (black earth and ivory), so the storm, even though it could be something bad, brings about a good change.