What a yellow alert means: the rainfall thresholds behind Kerala's colour-coded warnings

Background

Background to the yellow alerts now in force across seven Kerala districts.
The Kerala State Disaster Management Authority publishes the rainfall thresholds that go with each colour of warning issued for the State.
A yellow alert means isolated heavy rainfall is forecast, defined as 64.5 mm to 115.5 mm of rain within 24 hours.
The colours are a graded scale: a yellow alert asks the public and agencies to stay watchful, while higher colours signal heavier rain and a greater need for preparedness.
The alerts are issued district by district, which is why the list of districts under warning changes from day to day during a rain spell.
The Authority is the State's nodal body for disaster management, and its rainfall page carries the daily district warnings.