Sri Lanka, Nov. 7 -- Colombo received 129mm of rainfall within a few hours on Friday evening (November 6), according to the Department of Meteorology. Several roads flooded, and traffic across the capital slowed to a crawl during the evening rush hour. The 129mm is a reading from the Met Department's Colombo station, so not every part of the city would have received the same amount; some areas will have had more rain and others less.

The figure is easy to read out on the news and hard to picture. Put simply, 129mm of rain means 129 litres of water landed on every square metre of the city. That is six and a half 20-litre water cans emptied onto a patch the size of a small bathroom floor.

Latest update as of 12 pm (7th Nov):

The Disaste...