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Rain arrives in Perth after driest seven months on record

Perth just registered its driest October-to-April period on record despite a welcome burst of rain on Tuesday. 

Summer and the surrounding months are typically the driest time of year in Perth as cold fronts shift further south and rain-shielding high pressure systems become the dominant synoptic feature over southwestern Australia.

Image: Perth’s average monthly rainfall throughout the year.

However, even by Perth’s dry season standards, the last seven months have seen exceptionally low rainfall.

In an average pair of years, Perth would receive around 160 mm of rain between October and April. But over the last seven months, the city has only collected 23 mm, which is less than 15 % of the long-term average.

The past seven months have easily been Perth’s driest October-to-April period on record, beating the previous record of 48.8 mm from 2000-01, with data available back to 1880.

Perth's official rainfall total for the last seven months includes any rain that reached the city’s gauge between 9am on September 30 and 9am on April 30. This is because a meteorological rain day includes all rainfall recorded during the 24 hours up to 9am each day.

So, while Perth received some very welcome rain on Tuesday as weakening thunderstorms drifted south over the city, it all fell after 9am and was therefore officially counted as May's rainfall.

Image: Rain and thunderstorms over southwestern Australia, inclding Perth, on Tuesday, April 30.

As of 6pm AWST on Tuesday, Perth had received 6 mm of rain, which was the city's best daily rainfall in six mohths.