Police hold serious concerns for a woman missing in extreme heat in the harsh Pilbara outback for three days.

Police, SES, and members of the local community from the remote town of Tom Price started searching for 36-year-old Felicity Shadbolt after she failed to return from a walk around the Mount Nameless area.

The Tom Price local was last seen at 11:30am on Sunday.

Pilbara District Police Inspector Ray Thompson said the search continued at first light today, with about 35 people involved in the ground search, along with a helicopter with a spotter, and a fixed-wing aircraft with two spotters on board.

"We have horses on site today as of first thing this morning — it's going to be a very challenging day, so we've started at first light," Inspector Thompson said.

"We also have a helicopter and fixed wing aircraft and we've expanded the search to other areas to give us every best chance of locating her."

Police, SES, and community members from Tom Price have been searching on foot, horseback and helicopter for 36-year-old Felicity Shadbolt. ( Supplied: WA Police )

Adding to the challenge, and concern, is the extreme heat experienced in the region in recent days.

Daniel Hayes, observer at the Broome Bureau of Meteorology, said temperatures had soared to 46 degrees Celsius. The maximum temperature was due to hit 41C today.

"It has been a very hot period through the Pilbara, in particular, over the course of the last few days," Mr Hayes said.

"We've seen some temperature records in other parts not that far away [from Tom Price]."

The focus of the search is Mount Nameless, around 4km from Tom Price, where the missing woman is a regular walker. ( Supplied: WA Police )

The search was temporarily called off on Monday after storms rolled through the area, bringing wind, rain, and lightning.

Inspector Thompson said an Australian Maritime Safety Authority aircraft used infrared technology to look for Ms Shadbolt last night.

"They conducted a search pattern for three hours last night looking for any heat signatures that might resemble a person on the ground but unfortunately nothing was sighted in that search area," he said.

"We're very concerned — it's now been three days since she was last seen.

"All we can do at the moment is to do our best to both go over old ground and to continue our search into new areas.

"She's a very fit person — she does a lot of running — and that does make a big difference from your average walker or hiker who would normally limit themselves to a smaller area."

Forecast thunderstorms add to danger

The Bureau of Meteorology said there was a chance of further storms in the area in the coming days, which Mr Hayes said could cause flash flooding and bushfires from lightning strikes.

"We're only talking 30 per cent chance of showers and storms, fingers crossed there won't be anything that will get too much in the way, but there is a chance there," Mr Hayes said.

"Whenever you have a thunderstorm, regardless of what the most likely forecast is, there's always is a chance you get a big fall out of one of them.

"All in all, it's not a great situation for anyone to be lost in."