In regards to the Aztec,
In Andersen and Dibble's translation of the Florentine Codex there is a brief passage dedicated specifically to clouds. It is found on page 20, book 7.
When [clouds] billowed and formed thunderheads, and settled and hung about the mountain tops, it was said: "The Tlalocs are already coming. Now it will rain. Now the masters of the rain will sprinkle water."
The rest of the mention of clouds in the book is about how it heralds Tlaloc and his lords and the coming of the rain or how a rainbow signifies that rain clouds will lessen and dissipate
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