The temperature in the West Australian capital is set to reach 39C on Christmas Eve before climbing to 42C on both Christmas Day and Boxing Day.

That would make it the hottest Christmas period in Perth since records began more than a century ago, according to the Bureau of Meteorology, exceeding the 2007 period when the three-day average temperature was 40.3C.

The mercury on Christmas night is tipped to reach 27C and there is little relief on the horizon, with maximum temperatures set to remain in the high 30s.

Total fire bans are likely to be implemented, particularly throughout the southwest, with Fire and Emergency Services Commissioner Darren Klemm describing the forecast hot and windy weather as prime bushfire conditions.

"Everyone's got a role to play," he told reporters on Thursday.

"We want the number of fires that occur to be as small a number as we possibly can, and total fire bans is one way that we do that."

During total fire bans, people are banned from lighting campfires or bonfires including in backyards or from using fuel-powered lawnmowers, angle grinders or other powered tools.

The use of electrical or gas-powered barbecues is permitted as long as they have an enclosed flame.

Mr Klemm said he was confident the vast majority of volunteer firefighters would comply with a requirement to have had their first COVID-19 vaccine dose by December 31.

The weather bureau is also monitoring a tropical system in the Timor Sea which could develop into a tropical cyclone.

"There's a small chance that system will form into a cyclone and affect northern parts of the Kimberley from Sunday into the early part of next week," BOM WA manager James Ashley said.

Perth's hottest Christmas Day was 42C in 1968, with the temperature expected to match that this year.

Australian Associated Press