San Francisco. The fog. They are like a couple. But how to translate “fog” into French properly? Is it la brume? Or le brouillard? Both word describe the same meteorological phenomenon. So what is the difference? Well, it’s all about visibility. In French, we say brume when the visibility is between 1 km and 2 km, brouillard when it’s less than 1 kilometer. Knowing that, I’m sure that “fog” is best translated by the French word brouillard!