Joel speaks of wonders in the heavens and on the earth, including blood, fire, and columns of smoke. He adds that the sun will be turned to darkness and the moon to blood before the great and awesome day. See Joel 2:30–31.
In Joel 2:28–32, the speaker (Yahweh) promises a future “afterward” when God’s Spirit will be poured out widely, not limited by age, gender, or social rank. This inner empowerment is paired with outward signs: dreams, visions, and prophetic speech. These verses close a larger movement in Joel 2 that shifts from threat to hope. Earlier, the book describes devastating loss and calls the community to return to Yahweh with sincerity, then reports Yahweh’s compassion and a pledge to restore crops and remove shame.
These verses promise a future “afterward” when Yahweh pours out his Spirit widely, not just on a small elite. The text stresses breadth by repeating the list: sons and daughters, old and young, and even male and female servants (verses 28–29). The expected results include prophetic speech and other forms of God-directed insight (dreams and visions).
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Joel 2:30-31, then read the surrounding section so the answer stays connected to the passage's flow.
30I will show wonders in the heavens and in the earth: Blood, fire, and pillars of smoke.
31The sun will be turned into darkness, And the moon into blood, Before the great and terrible day of Yahweh comes.