Experts say there was a number of factors that contributed to the tragedy including the extreme weather, the location of the holiday homes and timing.

There was a large supply of moisture in the atmosphere from a tropical storm that had caused flooding in Mexico and then tracked north as it died out.

Kerr County, where the camp was located and where 75 lives have been lost, is a hillier part of Texas than surrounding counties. This meant that the moisture-laden air was forced upwards, building huge storm clouds.

These storm clouds were so large they effectively become their own weather system, producing huge amounts of rain over a large area.

This system was slow-moving, adding to the rain totals, and creating further thunderstorms along the area containing the Guadalupe River, which surged with unprecedented speed.

The National Weather Service reported a swathe of around 5-10in (125-250mm) of rainfall in just three to six hours across south-central Kerr County. Between Thursday and Monday there were nearly 21 inches of rain in some parts.

Average July rainfall over the last 25 years for the Kerrville area is just over two inches, which means around four months of rain fell in a matter of hours.

The timing also contributed to the loss of life - many Texans had gone to bed on the Thursday night unaware such a catastrophic storm would wake them in terror in just a few hours.

A flood watch had been issued on Thursday afternoon and after midnight local time it was upgraded to a flood warning, advising people to find higher ground.

In the next two hours it became a flash flood warning and some people have reported getting text alerts on their phones during the night.

At 3.30am, Kerrville City Manager Dalton Rice said he went for a jog near the river and it was only lightly raining.

Half an hour later, an emergency flash flood warning was issued for Kerr County, an alert from the NWS that this was a “particularly dangerous situation” alert, when major floods had already taken hold.

Camp Mystic was in a spot with some of the highest rainfall levels during those calamitous few hours.