In Australia, a heatwave is defined operationally as a period of at least three days where the combined effect of high temperatures and excess heat is unusual within the local climate (BoM 2012; Nairn and Fawcett 2013).

According to the Bureau of Meteorology, two aspects of this definition are important:

First, a heatwave is defined relative to the local climate, so a heatwave in Hobart is not the same as one in Alice Springs.

Second, the concept of excess heat needs to be taken into account because if overnight temperatures are also unusually high, there is no relief from the daytime heat. 

Right now the North Coast Public Health Unit is on high alert and has warned of the potential health risks associated with more predicted hot weather in coming days.

Public Health Unit Director Paul Corben said with hot summer conditions forecast it is important that people take precautions to prevent heat-related illness.

“Heat-related illness ranges from mild conditions to very serious medical emergencies. While heat-related illness can affect anyone, certain groups of people are particularly vulnerable.

“These include older people, infants and children, people with a chronic medical condition and those who live alone.

“During hot weather, it’s important to stay in regular contact with elderly neighbours, friends and relatives and to look out for other vulnerable members of their community.

“Heat puts a lot of strain on the body and can cause dehydration, heat exhaustion and heat stroke. It can also make underlying health conditions worse,” Mr Corben said.

“Being prepared and taking simple precautions reduces the risk of heat-related illness.”

In a report released by the Climate Council in 2014 entitled Heatwaves: Hotter, Longer, More Often, their findings showed there had already been an increase in both the frequency and duration of heatwaves between 1971 to 2008.

The report says that the number of hot days had doubled in the last 50 years with capital cities experiencing more intense hot weather than expected.

Southeastern Australia is highlighted as a particular ‘hot spot’ with increased risk of heatwaves, drought and bush fires, having as it does, both the highest population and urban density (ie: concentration of buildings, roads and cars, which all add to the heat) and hence radiant heat.

The continued accumulation of greenhouse gases in the atmosphere, primarily from the burning of fossil fuels, means more heat is trapped in the lower atmosphere, which increases the likelihood of heatwaves.

“If the current trend in greenhouse gas emissions continues through the rest of this century, today’s record-breaking hot weather will become commonplace, occurring almost every summer across the country,” the report states.

It continues, “The choices we make over this decade will largely determine the severity of extreme heat that our children and grandchildren will experience.”

RECENT WEATHER PATTERNS: A weak La Nina brings more summer rain

The cost of air-conditioning:

Finder.com.au crunched some numbers and found the cost of running one air conditioning unit is the same as running 25 standing fans.

Some other interesting finds:

* Using your fan for eight hours per night for the duration of summer will cost Aussies a total of $17, whereas using your aircon for the same amount of time will cost you $432. That’s a difference of $415, money which could be saved.

* 59 per cent of Aussies will actually crank both the aircon and fan this summer potentially wasting over $535 million collectively on luxury cooling.