Millions of Americans are under flood warnings after heavy rain this weekend in a large portion of the south and south-western US, where high waters submerged vehicles in Texas and swept hikers in Arizona off their feet.

Government meteorologists issued flood warnings for more than 13 million people after torrential rainfall created life-threatening conditions in a region including north-east Texas, Louisiana, Arkansas and New Mexico.

Western states, including Arizona, are currently dealing with droughts that threaten the water supply in the Colorado River, one of the state’s largest reservoirs.