So independent of any woo-woo, tarot cards are designed to be a potent conceptual microcosm. That means that when you shuffle the cards and do a reading, with a decent understanding of what each of the cards represents, you essentially make a little randomly generated conceptual perspective through which to view the problem. Extremely helpful for shaking out of an established mindset, finding an unexpected angle which reveals connections you hadn't considered.

I can't really speak to astrology, but I wouldn't be surprised if it turns out to be approximately accurate for some reason other than the stars themselves. Perhaps the changing temperatures of the seasons have a slightly noticeable effect on natal development.