积雨云，又名雷雨云，简写为Cb，属于低云族。

积雨云可以单独从积云状态发展出来，也可能是伴随冷锋面产生的，通常会产生强阵性的降水，并伴有大风、雷暴等。

积雨云是对流云发展的极盛阶段，云体浓厚庞大，云底混乱，颜色阴暗，有滚轴或悬球状，有时扩展达几千米宽，云底在3,000到4,000米左右，云顶可以向高空伸展，可达23,000米，相成蘑菇状，也可在低部5,000米处平衍，形成铁砧状，当云顶到达-15℃以下的高空时，水滴冻结成冰晶，呈现白色，云浓密时，云体出现闪电，云色昏暗。

积雨云会造成强降水，但一般只持续20分钟，如果当地太阳光强烈，降水会很快蒸发，在几千米以外形成新的云，有时会伴有冰雹和龙卷风。

Cumulonimbus, from the Latin cumulus ("heap") and nimbus ("rainstorm", "storm cloud"), is a dense towering vertical cloud associated with thunderstorms and atmospheric instability, forming from water vapor carried by powerful upward air currents. If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell. Cumulonimbus is abbreviated Cb and are designated in the D2 family.