Tens of thousands of people attending the Burning Man festival in the Nevada desert have been asked to remain indoors and ration their supplies of food and water after persistent heavy rainfall turned the site into mud bath.
Organisers warned festival-goers on Saturday: "If you are in BRC (Black Rock City), conserve food, water and fuel, and shelter in a warm, safe space."
They added that access to the site in Black Rock City has been closed "for the remainder of the event" because of flooding and mud.
The US Bureau of Land Management, the agency that manages the land on which the event takes place, said in a statement: "Rain over the last 24 hours has created a situation that required a full stop of vehicle movement on the playa.
"More rain is expected over the next few days and conditions are not expected to improve enough to allow vehicles to enter the playa."
Paul Reder, who has been attending the festival for 22 years, told Reuters news agency during a video call: "Fortunately we're in a fairly big camp with a lot of supplies.
"As a community, everybody's sharing with each other."
Mr Reder said he expected it would take at least two days for the area to dry out.
While he was prepared to ride it out, he said some attendees are leaving the site on foot and trekking to the nearest highway.
Heavy rainfall had a widespread impact across the state of Nevada on Friday, with the National Weather Service warning of flash floods up until Monday morning.
Black Rock City saw more than half an inch of rain drop overnight, organisers estimated.
Burning Man is a celebration of self-expression that culminates in the ceremonial burning of a towering 40ft effigy.
Its origins can be traced back to the incineration of an eight-foot wooden "man" on San Francisco's Baker Beach in 1986, which eventually evolved into an annual gathering in the Black Rock Desert.
Tens of thousands convene in the remote area in northwest Nevada each year for the event, according to the event's website.
The exact attendance figures for this year's festivities remain unclear, but local media reported there were more than 70,000 participants.
The event began on 27 August and is set to continue until 4 September.