The idea of signs representing particular weather patterns comes from the zodiacal signs meaning the same thing as months. We even find this in Chaucer's Canterbury Tales, where people think about going on pilgrimages when the blustery portion of March gives way to April's more moderate spring-like weather, and the sun is halfway through its course in "the Ram."
The earth-air-fire-water division is basically the Aristotelian elements. These alternate, along with the so-called male-female signs. (air-fire=male, earth-water=female.) This latter bit is really ancient, going back to a belief in a mother Earth and father Sky. We know them as Gaia and Ouranos (Uranus)
There is a debate as to whether the exaltations were Babylonian or Egyptian in origin. Possibly they diffused from Egypt to Babylon. Are you familiar with the work of Egyptologist and astrologer Joanne Conman?
Also, Ptolemy was a Renaissance Man-- prior to the Renaissance. He wrote extensively about the geography of the known world. He certainly read about places that he didn't personally visit, just as you might today.
Alexandria, Egypt is part of the Mediterranean climate zone, with cool rainy winters and hot rainless summers. It's not far from the true desert, but equally there was snow in the mountains of Greece, Iraq, and Lebanon. Educated Egyptians would have known about them. The onset and cessation of the rainy season would vary somewhat annually and in drought-wet cycles. Don't forget trade: Egypt was part of a Mediterranean network of trade that brought Egyptians into contact with the wider world.
Well, both the myths and the climate are a moving target. Myths vary over time and across nations. The climate varies with location. What holds them together is the concept of diffusion-- star and weather lore moving across places by oral or written transmission.
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I'll have to scrounge into my stash of scholarly artices when I have time, but the point being that the tropical zodiac comes into its own when the "scientists" of the day realized that the spring equinox was going to slip back into Pisces. (Try interpreting the New Testament in this light, incidentally-- a new deity who befriends fishermen, multiplies loaves and fishes, walks on water, stills the waves, and so on. Revelation ends with the Triumph of the Lamb-- i. e., the Aries equinox.)
What happens subsequently is that the sidereal equinox did move seriously back into Pisces. Because we don't know exactly what the equinox was back around 0 CE, it is guesstimated that today the two zodiacs are 24 or 27 degrees different.
