A heatwave in Western Australia’s Pilbara region has broken national records for late season maximum temperatures.

Temperatures above 40C have been recorded for several days straight due to a hot air mass over central and northern Western Australia.

On 23 April, Mardie broke the national record for the highest temperature so late in the season, reaching 42.8C, the Bureau of Meteorology said.

On 24 April, Marble Bar recorded 42.1C, the latest anywhere in the country had recorded a temperature above 42C. That was broken again a day later when Pardoo Station in the Pilbara region reached 42.4C.

Mandora then recorded 42C on 26 April.

The previous national record for late season heat was at Roeburn in WA, which recorded 42.1 C on 23 April 23 2005.

The long bout of extreme heat has extended through the Pilbara into inland parts of the Kimberley.

Darryl Vink, a duty forecaster with the bureau, said Monday was likely to be the last day of temperatures in the 40s, with a cold front expected to bring cooler air to the region this week.

Vink said it was “very late in the year” for such high maximums and the normal temperature range would be in the mid-to-low 30s.

“Roughly speaking, we expect it to start cooling down around March,” he said. “Change is coming. It’s the last of the hottest days through here.

“Once that cooler air starts pushing up from behind the cold front we’ll see a lot of that heat being flushed out.”

The bureau’s national climate outlook for May to July is for warmer than average daytime temperatures to continue across northern and eastern Australia. Elsewhere, May to July days have roughly equal chances of being warmer or cooler than average.

Nights are expected to be warmer than average nationwide.

The bureau expects wetter than average conditions for most of Australia for May to July.

The exception is parts of the tropical north, along the eastern seaboard and into southern Tasmania, where there are roughly equal chances of being wetter or drier than average.

A warmer than average eastern Indian Ocean, leading to increased moisture in weather systems across the country, is the main driver of this outlook.