Explaining the ‘unusually extreme’ rain and weather that caused Sydney’s fourth major flood in two years

NSW State Emergency Service respond as flood waters submerge residential areas following heavy rain in Windsor, Sydney on Tuesday. Photograph: Loren Elliott/Reuters

The fourth major flood to hit greater Sydney in less than two years had no single cause. It was triggered by a confluence of events that combined over the weekend to dump as much rain in some areas as Melbourne or London typically receive in a year.

The extent of the flooding was exacerbated by circumstances on the ground – a saturated landscape that was unable to absorb much more water after the wettest start to the year on record, and dams being close to full and unable to hold the downpour.