Why Melbourne’s summer was colder than usual

Melbourne has shivered through its coldest summer in 19 years, and climate change may be to blame.

Melbourne has just shivered through its coldest summer in 19 years.

Both the average daytime and overnight temperatures have been the coldest since 2002 – and the outlook for Autumn is for the cool times to continue.

The colder temperatures can be blamed on La Nina, which has prevented warm days from becoming super hot like Victoria usually swelters in most summers.

The mean temperature this summer was only 0.2C under the long term average – but because climate change is fuelling warmer weather, the summer we have just had has been much colder than any other in almost two decades.

Tom Saunders, the Chief Meteorologist at Sky News Weather, said it had been “particularly cool”.

“If you look at the maximum temperatures in Melbourne this summer, they have averaged 24.3C. That actually makes it the coldest summer since 2002.”

The minimum average temperature was 14.5C in Melbourne.

“Both the minimum and the maximum over the last few years have been around two or even three degrees warmer than what we have seen [this year]. If you look at the minimum and the minimums and take the average, we call that the mean temperature, which is 19.4C. And, no surprise, it’s the coldest in 19 years.”

The long-term average is 19.6C.

“Because it’s been so warm, thanks to global warming, that’s why it’s still the coldest in 19 years even though those temperatures where really close to the long term average.”

Mr Saunders said the rainfall had actually been lower than last year and was not far off an average summer.

“People might forget last summer was actually really wet.”

As of Wednesday evening, Melbourne was up to 138.8mm of rain. The long-term average was 154.2mm.

“It’s actually been drier than normal and it’s below last year where we picked up 197.6mm, so we are almost 60mm less than what we had last summer.”

Mr Saunders said it had been cooler – despite less cloud and rain – was La Nina that led to above average rain in NW Australia – an area dubbed the “heat engine”.

“That is where we normally see very hot temperatures and when we have a northerly airstream, that hot air moves down to Victoria. The rainfall in the heat engine has been about double, which has dropped the temperature … Meaning when we get the northerly winds, Melbourne’s temperatures haven’t been as hot as they have been in the last couple of decades.”

An example was last Thursday – northerly winds pumped the temperature to 31.8C, when on a normal summer it may have reached 40C.

It had been a similar pattern statewide, with close to average rainfall, and cooler temperatures, which is how the whole state would end summer.

“We have a cool spell due to southerly winds, so for the last few days of summer will be a good example of what we have seen – very little change from what we have seen.”

Autumn would also be impacted by La Nina. “It will be much cooler than previous years, and there is signal there it’ll be wetter than normal.”

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