Rain is on the way, but southern WA has seen one of its driest Augusts in more than 10 years.
Weatherzone.com.au meteorologist Sam Terry said a broad ridge of high pressure had extended over the southern states, including the south of Western Australia, stopping rain from reaching the interior and confining showers to the coast.
Mr Terry said Perth had only picked up 26mm so far this month.
He expected a trough would bring heavy falls today and tomorrow, which could lead to a further 10mm.
If the monthly total stays below 40mm, it will be Perth's driest August in 30 years.
Further north in Geraldton, which averages 65mm for August, only 1.6mm has fallen.
Mr Terry said showers this week could bring a further 25mm.
If the total stays below 27mm, Geraldton will see its driest August in 67 years.