Perth clocks hottest September day ever

Perth has had a glance into the summer ahead with its hottest September day on record.

But the West Australian capital is being warned the unseasonable weather doesn't plan on sticking around.

The thermometer hit 34.2 degrees Celsius about 3pm on Saturday, passing the record set in September 1918, when the temperature reached 32.7C.

But Perth's time in the sun is over for now with a cold front bringing moderate to heavy rain and damaging winds on Sunday.

"The temperature will drop to 23 degrees and lots of rain and wind," said Neil Bennett from the Bureau of Meteorology.

Residents in the southwest of the state, including Perth, have been urged to prepare their homes for the bad weather, with damaging winds up to 100 kilometres per hour predicted.

Mr Bennett said the rain would move east during Monday and be replaced by average September temperatures - around the 20C mark.