Joel describes it as “a day of darkness and gloom,” with clouds and thick darkness. The description highlights terror and overwhelming threat. See Joel 2:2.
In Joel 2:1–3, a public alarm is ordered from Zion because a decisive “day of Yahweh” is near. The coming event is pictured as overwhelming darkness and as an unmatched, powerful force moving across the land. This unit stands at the start of Joel 2, intensifying the crisis described earlier in the book. After widespread devastation in chapter 1, the prophet now shifts from describing loss to sounding an urgent warning that something even more threatening is approaching.
Joel 2:1–3 presents an urgent, public warning centered on Zion (Jerusalem’s temple hill). The trumpet and alarm signal a crisis that concerns the whole community, not a private spiritual experience.
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 2:2, then read the surrounding section so the answer stays connected to the passage's flow.
2A day of darkness and gloominess, A day of clouds and thick darkness. As the dawn spreading on the mountains, A great and strong people; There has never been the like, Neither will there be any more after them, Even to the years of many generations.