Australia Weather News

Temperatures have been plummeting in large parts of the country as Australia closes in on the shortest day of the year, the winter solstice.

On Friday morning, widespread frosty conditions spread across large parts of New South Wales and Victoria, and some parts of Queensland.

Cold air and clear skies combined saw broad areas drop to sub-zero degrees, with the Bureau of Meteorology (BOM) recording some of the coldest temperatures in two years in several locations.

"This is definitely the lowest temperatures that we've seen this year [for some]," BOM senior meteorologist Miriam Bradbury said.

"But that makes sense as we've moved into the beginning of winter, and typically that sort of June, July period is the coldest for most parts of Australia."

But during the depths of winter, which town actually holds bragging rights as the coldest in the country?

We've asked the BOM's climate team to open up the history books and take a look at the stats.

Turns out the answer is similar to what's unfolded this week.

Defining 'coldest' is tricky

First, let's start with the definition of "coldest", because there are quite a few ways to answer it.

We've looked at two different metrics.

The BOM looked at its available records for July, which is the coldest month of the year.

We've also defined a "town" as having more than 1,000 people, in line with the Australian Bureau of Statistics definition of an "urban centre".

So, sorry to Liawenee, Tasmania — population two — which is the true coldest permanently inhabited place in Australia, but you'll have to sit this one out. We're also going to exclude the Alps, because everyone knows it's cold there.

Based on overnight temperatures in the depths of winter, Australia's coldest town is Cooma in southern New South Wales.

During July, the town — known as the "capital of the Snowy Mountains" — averages minus 2.6 degrees Celsius at night, and -2C at the airport, according to figures from the BOM.

"Anything elevated is going to be cooler because the temperature does decrease with height. It's always cooler up on the mountains than it is down in the lower-lying areas," Ms Bradbury said.

"So Cooma, because it's got that little bit of elevation at 800 metres, it does generally see a cooler climate than some of those lower-lying areas."

This week it has certainly been living up to that reputation, falling to -7C this Thursday and -8.5C on Friday.

An honourable mention also goes to Walcha, in the Northern Tablelands region of New South Wales, which wasn't far behind with a July average minimum of -2.2C.

So that's the overnight temperature. But what about during the day?

With that lens on, the title of coldest town stays in New South Wales — this time, going to Oberon in the Central Tablelands.

During July, its temperature doesn't even make it into the double digits, peaking at between 8.1 and 8.8Con average, according to BOM figures.

Add a bit of wind chill into the equation, and it's likely to feel even colder.

"When it's windier, it feels colder. When it's more humid or the dew point temperature is higher, it tends to feel warmer," Ms Bradbury said.

It just so happens that the coldest place, by average temperature, is a draw between both Oberon and Cooma.

So if you're looking for a tie-breaker, you're out of luck.

Of course, there are a lot of places in Australia that either don't have observations or haven't had weather station data for as long as others. It means there may be colder places out there, but there is just no good data to back it up.

For the record, the coldest temperature ever recorded in Australia was at Charlotte Pass.

On June 29, 1994, it dropped down to -23C at the Kosciuszko Chalet.

The coldest temperature ever recorded on Earth was set at Vostok Station, in Antarctica, which dropped down to -89.4C on July 21, 1983.

What makes one area colder than another?

Ms Bradbury said both Oberon and Cooma were good examples of the type of features that made a town cold.

In general, our coldest winter places are elevated and far enough south that they feel the effects of the winter fronts coming through. They also tend to be inland.

"At this time of year, once the sun goes down, especially if we have a clear night, the temperature drops very quickly over land," she said.

"But the water will hold its heat a little bit more, and that, in turn, will make those coastal locations just a touch milder than inland."

During the summer months, on the other hand, it's the coastal areas that are usually the coolest.

"It's sort of the inverse of the situation," she said.

"You're more likely to get the sea breezes, and, you know, the heat is sort of retained a little bit more over the land."

How the winter solstice affects the cold

This Saturday marks the Southern Hemisphere's winter solstice — the shortest day of the year.

It signals the point at which the hemisphere is tilted furthest away from the Sun, meaning fewer daylight hours.

But the coldest time of the year is still to come.

This means the coldest temperatures are typically a few weeks after the shortest day of the year.

Having said that, the weather can always throw a spanner in the works, according to Ms Bradbury.

"Weather is what you get, whereas climate is what you expect," she said.

In terms of the current run of cold weather, Ms Bradbury said the frigid mornings would continue throughout the weekend until a cold front arrived, stirring up strong winds and the possibility of severe weather warnings.

The front is expected to reach Western Australia today, and then take the weekend to move across the Bight.

"So as we go into early next week, we've actually got a couple of fronts whipping through, which are going to keep conditions fairly windy," she said.

"We may see severe weather warnings for damaging winds issued, both ahead of and behind the front. The winds are looking very strong."

Notes about the data:The statistics for July are based on 1961-1990 averages for those sites that have sufficient data in the 1961-1990 period, and all available years of data otherwise. Note that some sites are no longer operational.