Tropical Storm Hilary has drenched Southern California from the coast to the desert resort city of Palm Springs, forcing rescuers to pull several people from swollen rivers, before heading east and flooding a county some 64 kilometres outside of Las Vegas.

The National Hurricane Centre in Miami downgraded Hilary to a post-tropical storm Monday morning but warned that “continued life-threatening and locally catastrophic flooding” was expected over portions of the southwestern US along with “record-breaking” rainfall and potential flooding in states as far north as Oregon and Idaho.

Remnants of the storm that first brought soaking rains to Mexico’s arid Baja California Peninsula and the border city of Tijuana were expected to linger at least through Tuesday morning.