In Chinese we often describe impos-sibilities as "grain from the sky and horses with horns," or just "raining rice." But nowadays Taiwan often sees acid from the sky. In fact, more than 57 % of the rain that falls on Taiwan now has a pH of 5.0 or less, the official threshold for acid rain.
成語「天雨粟、馬生角」，以「天降米粒」比喻不可能的任務；不過在台灣，天雨「醋」卻是司空見慣的常事，因為我國有高達 57 % 的降雨，是屬於酸鹼度在 pH 值 5.0 以下的「酸雨」。