Torrential rain in July 1994 caused the collapse of a retaining wall at the Kwun Lung Lau Estate building in Kennedy Town, killing five people and necessitating the evacuation of two thousand families. In August 1995, heavy rain following the passage of Severe Tropical Storm Helen brought widespread landslips, killing three persons on Hong Kong Island. Thunderstorms, which may or may not be accompanied by heavy rain, are localised phenomena. It is possible for intense thunderstorms to pass very close without any effect and thunderstorms that appear to be approaching often die out before they arrive. Also, a thunderstorm affecting one part of Hong Kong may not affect other parts.
Lightning can damage electrical installations, start fires and cause death by electrocution.
Violent gusts often occur in squall lines associated with thunderstorms. Boats are known to have capsized in squalls. Windshear associated with squall lines is also a potential hazard to aircraft during landing and take-off. Under certain favourable conditions, thunderstorms may give rise to intense columnar vortices in the shape of funnel clouds reaching the ground or the sea. These vortices are known as tornadoes or waterspouts depending on their occurrences over land or sea respectively.