Sommerregen literally translates to "summer rain". It's a compound noun that evokes a specific, often pleasant, image.
In the song, Vanessa Mai uses "Sommerregen" as a beautiful metaphor: "Und wie'n warmer Sommerregen / Wischst du die Spuren meiner Tränen einfach weg" (And like a warm summer rain / You simply wipe away the traces of my tears). It's an evocative and poetic word that suggests comfort, cleansing, and a gentle renewal, making it memorable and unique in this context.
Vanessa Mai sings to her own reflection, working up the nerve to actually look at it. She opens with the line everyone hands you when you're struggling — "Es sagt doch immer jeder, 'Vergib' dir deine Fehler'" ("Everyone always says, 'Forgive yourself for your mistakes'") — and admits it hasn't fixed anything. What she wants instead is the mirror itself: "Spiegel, Spiegel an der Wand, Lüg' mich bitte nicht so an" ("Mirror, mirror on the wall, please don't lie to me like that"), asking it to show her who she really is because she's stopped recognizing her own face.
The chorus keeps circling back to that same demand, with one small image tucked into the verse between them — "Wie'n warmer Sommerregen wischst du die Spuren meiner Tränen einfach weg" ("Like a warm summer rain, you simply wipe away the traces of my tears") — love doing quietly what an apology never could. By the last verse she drops the old excuse for good: "Es spielt keine Rolle, wer ich gestern war, denn ab heute seh' ich klar" ("It doesn't matter who I was yesterday, because from today I see clearly"). The mirror finally answers back.