Perth weather delivers coldest day in 50 years, wettest winter since 1996

Western Australia is once again showing off extremes on both ends, with the south-west shivering through its coldest winter day in a generation while parts of the north swelter under near-record heat.

The calendar may say spring is only a week away, but it certainly doesn't feel like it for much of the state.

On Monday, the Perth metro area recorded a daytime maximum temperature of 11.4 degrees Celsius, its coldest day in more than 50 years since the figure was reached in July 1975.

And no, we're not talking about Perth in Scotland.

The WA capital was forecast to reach a high of 14C but hadn't even made it to the double-digit mark until 2pm.

The city's previous coldest day so far this winter was July 28, when the mercury reached 13.9C.

Maximum temperatures were also 5 to 10 degrees below average across western parts of the state.

That included Bickley, which was on track to beat its lowest maximum August temperature of 9.4C, reaching a top of 8.3C just before 3pm on Monday.

The Monday low became official on Tuesday morning, with daily temperature records compiled by the Bureau of Meteorology (BOM) over a 24-hour period from 9am to 9am.

Why is it so cold?

The late winter chill is thanks to a pool of cold air moving through the south-west, which has delivered some locations their coldest day this winter.

So what exactly is a cold pool?

"Basically, we have cold fronts that come through and a cold front is a boundary between warm air ahead of it and cold air behind it," BOM senior meteorologist Jessica Lingard said.

"The cold pool is basically the cold pool of air that sits behind a cold front."

Perth remained cold on Monday as the cloud cover mostly prevented the sun from coming through and warming temperatures up.

The cold pool stretched as far north as Geraldton and Meekatharra.

When is the cold going to end?

Don't pack those extra blankets away just yet.

As that cold air mass slowly moves in an easterly direction, we can expect things to warm up across the state on Tuesday.

But lingering showers for the next two days mean maximum temperatures aren't expected to really heat up until later this week.

"We’re aiming for a top of 16C [Tuesday], heading to 20C for both Saturday and Sunday, the last days of winter and then Monday, the first day of spring, a sunny top of 22C," Ms Lingard said.

A different story up north

While much of the southern half layered up, folks across the Kimberley were sweltering under warmer-than-usual conditions.

Parts of the region saw temperatures soar five degrees or more above average for the month.

Wyndham Airport reached a steamy 38.5C, and Kununurra Airport not far off at 38.1C, their warmest days since early March and only about two degrees off their hottest August temperature.

The warm weather is expected to stick around for at least the next week.

What about all that rain?

The cold front that moved through WA's south-west on Sunday not only brought chilly temperatures, but strong winds and heavy rain.

Perth recorded a decent 20.2 millimetres of rain in the 24 hours to 9am on Monday, pushing its monthly running total to a healthy 169.8mm.

More falls yesterday added another 7mm, with lingering showers expected to continue over the next couple of days.

Ms Lingard said little rain forecast for the rest of August would mean we "might struggle" to exceed the Perth metro rainfall August record of 186mm, but it still remained a statistic to watch.

"We could be nudging close to our wettest August," she said.

The city has exceeded its average rainfall in each of the three months of winter for the first time since 1996.

While missing data for the metro gauge during June and July means we can't know the exact rainfall total for the season so far, BOM's climatology team has calculated the figure to be just over 500mm, taking into account nearby stations.

That made it the wettest winter since 1996 when 555.8mm was recorded.

Most of the south-west corner received 24-hour rainfall totals between around 10mm and 25mm to 9am Monday, with some places receiving more than 40mm.

Ms Lingard said rain over the weekend in parts of the Gascoyne and Pilbara were caused by a feature known as a north-west cloud band.

"We had a cloud band that thickened up late last week and on Saturday some significant rainfall fell between 20 and 30mm," she said.

A 96-year-old record for August rainfall was broken at a gauge at Yaleen, near Pannawonica — it saw more than 30mm of rain across the month.

The showers will stick around for a little longer but won't be adding much to the gauges.

As we move into the final days of winter, conditions will be mostly dry and settled across the state.