Friday, January 8, 2010

Heatwaves in Australia

There is no universally accepted definition of a “heatwave” so to a certain extent we can make up our own. A simple and easy to remember definition is the 5/5 rule – that is five days in a row where the maximum temperature is five or more degrees Celsius above average.

But academic definitions aside, one thing is eminently clear – heat waves are lethal happenings – in fact the most deadly of all meteorological extremes. Perhaps surprisingly, heat waves kill many more people each year than tropical cyclones, bushfires, thunderstorms and floods. Whenever there is a heat wave there is an immediate spike in community mortality, and from analysing the nature of the “spike” experts can estimate the associated death toll.

Australia has experienced numerous recorded heatwaves and some of the main events are listed here together with the estimated number of deaths recorded nationally:

* January 1908 - 246
* February 1921 - 147
* January 1927 - 130
* January 1939 - 438
* February 1959 - 105
* January 1973 - 26
* February 1981 - 15
* February 1993 - 17
* February 2004 - 12
* February 2009 - 374

The temperature profile of the Melbourne heatwave of January and February 2009. Note the three consecutive days over 43C in late January, followed by a record 46.4C on February 7. It is believed that 374 people died as a result. Melbourne's average maximum temperature for this time of the year is 26C.
Image: Wikipedia Commons.
(Click on image to enlarge)

These mortality numbers cannot be used to directly gauge the severity of heatwaves as the population and social habits of the day also play a role. The larger number or people around today will obviously produce a proportionate increase in mortality compared to the situation of say fifty years ago.

But on the other hand, people today have far more access to fans and air conditioning than their earlier counterparts. Direct comparisons are therefore difficult.

Australia’s southern capitals are all subject to heatwaves, including Perth, Adelaide, Melbourne, Canberra and Sydney, and these events are often accompanied by severe bushfires.

An interesting article appeared in the Melbourne Argus on Friday 19th January 1934 that contained some recollections of severe heatwaves in Melbourne over the years. The temperatures quoted are of course in the old Fahrenheit scale – 100 degrees Fahrenheit is approximately 38 degrees Celsius.

“A very good idea of the intense heat of Thursday (January 25th 1875) may be gathered from the fact that a gentleman of Soldiers Hill who thought it unnecessary to have a fire in the house to provide himself a meal utilised the suns rays to cook an omelette and the feat was successfully performed. He placed a school slate for a while out of doors then spread some butter upon it and breaking an egg thereon in a few minutes the egg was, perfectly cooked, as if done in the orthodox pan over a fire.

The Weather Bureau record on that day was 110.4 degrees, compared with 102.5 degrees yesterday. There were bush fires all over Victoria then; there were four days of intense heat in Melbourne, and it was reported that a stack of firewood had been ignited by the heat of the sun’s rays. As usual in a heat wave in those days the Yan Yean supply failed in most of the suburbs and water was carted in drays to Emerald Hill (South Melbourne) Richmond and

In 1883 the Hon. Ivo Bligh's cricket team was visiting Melbourne, on three days the temperature exceeded 100 degrees - twice it exceeded 104 degrees. Correspondents wrote to the newspapers of the odour of the filthy Elizabeth street drain-and the Yan Yean failed. For the next heat wave, in 1898, there was also an English team present and "Observer" wrote in his introduction to the account of the match, ' On every hand there were heard weary sighings for rain - rain by the inch even though Australia lost the cricket match because of it!” Almost the whole of Gippsland was ablaze. In Melbourne the horses of the Fire Brigade were exhausted and none could be found strong enough to take their places. Elms, planes, oaks, and willow trees withered in the parks in the first days of February.

In 1905 some persons walked through the streets of the city in bathing suits when 108.5 degrees was registered on two days in January - but bathing suits then were different. Amusements were postponed and labourers were forced to cease work.

The record heat wave in Melbourne, however, was in 1908 from January 15 to January 20, six days of “centuries" with a maximum of 109.1 degrees. There were many sudden deaths from heat-stroke; the heat hastened the deaths of many sick persons; there was a constant stream of ambulance wagons to the Melbourne Hospital, and the number of deaths was so abnormal that the Melbourne General Cemetery management was unable to keep pace with the demand for burials. The Yan Yean failed again though not so seriously. The heat was so intense in the Newport railway workshops that portions of it were closed. Schools postponed their opening after the Christmas holidays, stock and poultry died. Thousands of suburban residents left their homes and carried mattresses into the public parks. The tram and train services could not cope with the crowds who went to the beaches, and thousands were left stranded at St Kilda and Brighton beaches unable to obtain a foothold on the last trams and trains to their homes.

In February 1912 when there appeared the first report of a man and his wife having driven to the beach wearing bathing suits in a “motor landaulette”. Birds, beasts and even fish in the lakes dropped dead. Since then the heat and its effects have been more mild. A constable collapsed on Flinders Street station in 1922. In 1927 the most serious effect of 104.5 degrees in the shade after a run of hot weather, was that potatoes suffered from sunburn; two years ago a temperature of 108.9 degrees was registered at the Weather Bureau, and many persons suffered from heat-stroke”.

Even in modern Australian society with its air conditioning, fast communications and advanced medical practices, heat waves remain a summer menace, and with the experts predicting an increasing frequency, this is a menace that will probably get worse rather than better.


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  3. On the new BoM heatwave pilot it lists 3 levels, but what makes each level? Is it temps above average or something else? I only want to know because where I live we will be having (including today) a forcast 8 days above the old century including 4 days above 40, yet is only listed as severe, where as melbourne is classed extreme with 1 day above 40 and 4 days above 37

  4. Hi Nicky;
    The BOM appear to be using a complex algorithm based on the following direst quote:
    Heatwave intensity is a function of the maximum and minimum temperature over a three day period and how this relates to climatology at every location, including how this function has changed over the last thirty days.

    In other words the heatwave intensity identifies unusually hot conditions sustained for three days. The service also considers conditions over the preceding thirty days to include the degree of acclimatisation which may exacerbate or ameliorate the significance of the heat.

    "Unusually hot" is not defined in the public statement. At Sky News we presently use a simpler definition - 5 days or more where the maximum temperatures are 5 degrees or more above the long term average maximum. This definition does not take into account minimum temperatures or preceding conditions.

  5. Are you able to tell me I there was very hot weather around Dec 1921 or early 1922 please?

  6. Hi Robyne;
    What general location are you interested in?