What types of signs are given by the "lights in the expanse of the heavens"?

On the fourth day, God created lights in the expanse of the heavens for "signs", among other things. > Then God said, “Let there be lights in the expanse of the heavens to separate the day from the night, and **let them be for signs** and for seasons and for days and years. Genesis 1:14 NASB I understand the astrology seems to be forbidden in the Scriptures: > You shall not eat anything with the blood, nor practice divination or soothsaying. Leviticus 19:26 NASB. So, what specific signs are referred to here?