(1) Rain of 16 mm or more in 1 hour;
(2) Rainfall of 50 mm or more in 24 hours. Starting from the use of rainwater and the prevention of floods, it is divided into general rainstorm, heavy rainstorm and extreme rainstorm according to rain intensity. Due to the different topography and water conservancy facilities in various places, the consequences of heavy rains of the same intensity are also different. Therefore, the standards for heavy rains and extreme heavy rains are not consistent.
But in most cases it is divided according to the following criteria:
(1) A rainstorm with a rainfall of less than 70 mm in 12 hours or a rainstorm of less than 100 mm in a 24-hour period is called "general rainstorm".
(2) A 12-hour rainstorm with a rainfall exceeding 70 mm but less than 140 mm, or a 24-hour rainstorm with a rainfall of more than 100 mm and less than 200 mm is called "heavy rain".
(3) Any rainstorm with a 12-hour rainfall of more than 140 mm or a 24-hour rainfall of more than 200 mm is called "extraordinarily heavy rain."