India, Aug. 14 -- In August 2018, Kerala faced one of the worst floods in its history although this isn't reflected in the annual rainfall data for the state. According to the Centre for Monitoring Indian Economy (CMIE), which has annual rainfall data from 1902, total rainfall in Kerala in 2018-19 was 3164.1 millimetres (mm). This is the 34th highest annual rainfall in the state, nowhere near extraordinary. So, why did the floods happen?

A shorter time window presents a clearer picture.

Again, according to CMIE, which has weekly and monthly rainfall data from 1989, there was nothing out of the ordinary about the rainfall in June, July, and September (three of the four months that are considered the monsoon season in many parts of India;...