After escaping the worst of the heatwave that has scorched eastern Australia this month, the mercury is on the rise in southwestern parts of Western Australia.

Perth is set to swelter this weekend, expecting to reach 39 degrees on Saturday and 40 degrees on Sunday. This would be its hottest pair of days since January 25th and 26th, two years ago.

Geraldton has heated up very quickly after a mild start to the day. Despite the minimum of 15.5 degrees at 5:30am, it had cracked 40 degrees by 10am, and has continued to rise to a top of 42 degrees. It will likely be just as hot, if not hotter, on Sunday.

Further inland, this period of heat will likely last a day or two longer. Southern Cross is expected to hit 40 degrees or higher on Sunday, Monday and Tuesday; the first time there in the last four years.

Fortunately for Western Australians, a cold front and low pressure system will cause an abrupt end to this heat pulse from Tuesday and Wednesday. In Perth, daytime temperatures will swing from 9 degrees above average this weekend to 8 degrees below average on Wednesday, topping out at just 23 degrees.