If an event is imminent, it will happen very soon — hours or days, not 'someday' — and it often feels as if it is hanging over you. News uses it for danger: an imminent attack, imminent collapse, imminent death. Weather people say rain is imminent. It is a serious-sounding adjective; calling lunch imminent would usually be a joke. Though actually, the old Latin picture is 'to overhang', like a rock above your head, which is why the word still feels a little threatening even when the event is only rain or a deadline. You would not use it for something pleasant and far off. Formal enough for news; ordinary enough for a worried conversation.