The Bureau of Meteorology has issued a heatwave warning for parts of WA this week including Perth, Rockingham and Mandurah.
Perth is forecast to hit 38C on Monday and 37C on Tuesday through to Thursday.
It will be slightly cooler in Mandurah and Rockingham which is forecast to reach 33C on Monday, 32C on Tuesday and 34C on Wednesday and Thursday.
Bureau Meteorologist Jessica Lingard said a run of hot temperatures are quite unusual for this time of year.
"It's maybe not unusual to see a day or two of these warmer temperatures but to see an entire week this late into the month is perhaps a little unusual," she said.
"For around the Perth area it has been about 40 years since we last saw a week of really hot temperatures at the end of March and there are similar statistics for around the Mandurah and Rockingham areas."
Temperatures will drop slightly from Friday into the high-20s and low 30s.

PIC: Bureau of Meteorology
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