Faire la pluie et le beau temps

Literally: To make the rain and fair weather

Example: “Dans cette entreprise, c'est le directeur financier qui fait la pluie et le beau temps.” — In this company, it's the finance director who calls all the shots.

English equivalent: To call the shots

Origin: On record from 1732, and reaching back further for its logic than the date suggests. Weather has stood for divine or superhuman power across many mythologies — a god able to darken or clear the sky at will was, by definition, a god worth fearing — and Paris kept its own local version of the idea in Saint Geneviève, credited with the power to end both drought and flood by her intercession. Voltaire, writing on magic in his 1756 Essai sur les mœurs, traces the same instinct to the magi of ancient Chaldea, who he says searched for the cause behind rain and fine weather alike. Someone who fait la pluie et le beau temps today has exactly that older kind of unanswerable authority, minus the theology.