Despite the varying climate, the capitals – outside of Darwin – all have one thing in common.
They’ve just shivered through what is historically their coldest week on the calendar.
So why, in our massive country, is the coldest calendar week of the year so similar?
And does it mean the worst of the cold weather is now over?
What’s the coldest week for each capital city?
Firstly, let’s take a look at the stats for what is the coldest week for each of the capitals, according to the Bureau of Meteorology (BOM).
As you can see it’s right about now for all the capitals apart from Darwin, which has its coldest week in June.
Brisbane is the earliest, with its coldest week beginning on July 4, while Melbourne starts the latest – just four days later – with its coldest week beginning July 8.
When it comes to overnight temperatures however, which includes those chilly mornings which eastern Australia has been subject to recently, the “typical” coldest week is still to come for a few of the capitals.
Role of the winter solstice
The winter solstice — also known as the shortest day of the year — occurred three weeks ago, meaning the days are now getting longer.
So why is our coldest week of the year now, and not then?
According to BOM senior climatologist Simon Grainger, it has to do with the relationship between direct heating from the sun and the ocean temperatures, which continue to cool right up until spring.
“The shortest day of the year occurs at the winter solstice, and in the Southern Hemisphere it occurs each June between the 20th and 22nd,” Dr Grainger said.
“However, it takes some days or weeks for the land and oceans to catch up with the solar cycle, as these store and release heat through the year.
“Water cools down and warms up much more slowly than air, so sea surface temperatures continue to decrease around Australia into spring.
“For southern parts of the country, colder water means that even as the sun begins to warm the Australian land mass, southerly winds can still transport cold air over Australia, leading to late-season cold spells.”
The reason Darwin is a bit different is that cold outbreaks rarely affect the tropics, according to Dr Grainger.
While the coldest day of the year in Darwin tends to occur at the end of June, he said it can also happen from October to April, during the city’s wet season, when there are big days of rain and cloud cover.
Cold, wet and gusty week ahead
Unfortunately, making it to the other side of the “typical” coldest week of the year doesn’t guarantee the worst of the cold is behind us.
The randomness of individual weather systems means every year is different.
In the case of this year, BOM senior forecaster Dean Narramore said the week ahead was forecast to be much colder for much of eastern Australia, due to a deep low-pressure system spinning off the coast of Tasmania.
“That’s bringing widespread rain and strong and gusty winds, possibly damaging, through parts of eastern Tasmania, and some of that rain and winds also moving into southern parts of Victoria as well,” he said.
By mid-week, he said maximum temperatures were also forecast to be between 4 and 8 degrees colder than normal across New South Wales and Queensland.
Meanwhile, Western Australia and northern Australia will start the week off with milder weather, ahead of a large cold front hitting WA’s south-west on Thursday.