The rate at which rain falls, usually measured in millimetres per hour. Intense rainfall is associated with convectional rain, notably in thunderstorms and tropical regions, where intensity may be over 100 mm per hour. (British rainfall intensity is normally of the order of 2 mm per hour.) The intensity of rainfall is normally inversely proportional to its duration. Denault et al. (2006) J. Am. Water Resources Ass. 42, 3 examine the potential impacts of increases in short duration rainfall intensity on urban infrastructure.