With 40 dead and a disaster declared across all 50 city districts, experts warn extreme flooding will only worsen across south-east Asia

Bangkok is used to absorbing the sudden afternoon downpours that inundate the city during the rainy season. Even streets in many central high-rise districts can briefly turn into rivers, with rats and cockroaches racing out of sewers and taking temporary refuge on trees and buildings as the subterranean world is flushed out.

But every city has a breaking point, and this year rain fell so fast and so hard that whole neighbourhoods of the Thai capital have been transformed, not into rivers, but stagnant lakes. In parts of the city, roughly 300mm of rain - the equivalent of half a year of average rainfall in London - fell in about two days.