If we accept that science - in spite of all its impressive list of achievements - does not have all the answers for all the phenomena, and therefore scientific validation is not the only test of what is true or real, then Astrology is definitely true in the hands of a skilled practitioner.
There are numerous cheats and charlatans among astrologers who help in getting it discredited, but I have come across some very dedicated and brilliant astrologers who provide yeoman service in their own quiet way and in doing so establish the power of astrology. In the hands of such practitioners, astrology can definitely predict the future with such clarity and insight that you are left with no choice but to believe in it.
Astrology is very loosely used to mean everything from the weekly astro column to horoscope readings to tarot cards and crystal ball gazers. I have experience and some understanding of vedic astrology or Indian astrology so what I have said applies to vedic astrolgy specifically and not to the other forms.