nounBlack rainstorm signal (very heavy rain) [level 3].
noun"Hong Kong Observatory rainstorm warning system" 香港天文台暴雨警告系統 : there are three levels of warning: [level 1] 黃色暴雨 Amber rainstorm signal (potential heavy rain), [level 2] 紅色暴雨 Red rainstorm signal (heavy rain), [level 3] 黑色暴雨 Black rainstorm signal (very heavy rain).