Too much water all at one time.

More than 5,000 people are known to have died and thousands more are missing after devastating floods swept through the Libyan port city of Derna.

Entire neighbourhoods disappeared into the sea as a huge tsunami-like torrent of water swept through the city. Whole families were washed away, according to a Libyan journalist who has been speaking to survivors in the city, and who described the situation as “beyond catastrophic”.

A river runs from the mountains through Derna to the Mediterranean, and two dams on that river collapsed, so the city was like a dollhouse hit by a firehose.

The storm – a Mediterranean hurricane-like system known as a medicane – brought more than 400mm of rain to parts of the north-east coast within a 24-hour period. That is an extraordinary deluge of water for a region which usually sees about 1.5mm throughout the whole of September.

Is it climate change? As usual, it’s not possible to brandish fingerprints that remove all doubt, but climate change is expected to cause things like Unusually Heavy Rains, so there you go.