A search is underway for a 69-year-old German tourist who was last seen on Saturday while hiking in the Mount Augustus area, about 850 kilometres north of Perth.
The man set off on the hike with his wife on Saturday morning before the pair lost sight of one another.
She returned to the vehicle mid-afternoon, but became concerned when her husband did not return.
WA Police said the woman received help from other tourists in the area to try to find her husband, before authorities were notified.
The Australian Maritime Safety Authority conducted an air search of the vast site on Saturday night and Sunday, with the Karratha Police Air Wing also travelling to the area to help with the search.
Searchers have told the ABC they expected temperatures on the ground to reach the mid-40s on Sunday "without a doubt".
Officers from a number of police stations in the region are involved in the search with State Emergency Service volunteers from around the region also joining the effort.
Mount Augustus stands 2.5 times taller than Uluru, and is sometimes touted as the world's largest monolith, but many experts argue that is not the case because it is made up of multiple rock types.
The walk to the summit can take anywhere between five and eight hours, and the WA Department of Parks and Wildlife advises that climbers should have a "high level of fitness".
