CHILLING: Roman (7) and Teah (9) Smith, from Duffy, cool down in the lake at Weston Park on Monday. Photo: Rohan Thomson
Severe heatwaves were once expected to hit Canberra about once every 25 years, experts say, but the sweltering conditions forecast for this week will be the third such hot spell in the capital in four years.
And the blistering heat is a sign of things to come, with the CSIRO predicting ACT residents could suffer through 26 days a year with a top temperature of 35 degrees or more before the end of the century.
Health authorities are warning Canberra residents to remain indoors, stay hydrated and to check on vulnerable friends and neighbours as the mercury rises this week.
The ACT Ambulance Service will consider reducing its non-urgent patient transfers if the workload created by an expected heatwave becomes too great.
The Bureau of Meteorology is predicting a maximum temperature of 37 degrees on Tuesday, 39 degrees on Wednesday and Thursday, and 38 degrees on Friday.
There may be some showers over the weekend, but the rain will do little to lower the temperature, with a top of 37 degrees predicted for Saturday and 31 degrees for Sunday.
Bureau of Meteorology forecaster Sean Carson said severe heatwaves similar to the one predicted for this week had been recorded in Canberra in 1952, 1979, 2009 and 2013, and climate change was at least partly to blame for the increased frequency of extremely hot weather.
CSIRO senior researcher Penny Whetton said according to a long-term average, Canberra experienced five days a year with temperatures of 35 degrees or more.
But by 2070 scientists expect Canberrans to suffer through between 10 and 18 such days, or, allowing for all uncertainties, between 8 and 26 days.
Dr Whetton said the bureau had been recording Australia's temperatures for many years and exceptionally hot weather did occur every now and then. But that did not mean scientists could not identify trends towards warming caused by human activity.
''Because the background climate has warmed, when we get the conditions that are just right for very hot weather, the weather is a little bit hotter than it would otherwise be,'' she said.
ACT chief health officer Paul Kelly said the elderly, the obese, babies, young children and pregnant women were all at high risk during heatwaves.
People with a disability and people taking medication that may increase dehydration were also at risk.
Dr Kelly said danger signs of heat stroke included vomiting, headache, dry skin, feeling disoriented and falling unconscious.
He urged elderly Canberrans or those with low incomes who feel they cannot afford to cool their homes to head to shopping centres to take advantage of the airconditioning.
ACT Libraries is also encouraging people to escape the heat at their local branch this week.
ACT Ambulance Service chief officer David Foot reminded people never to leave children or pets alone in a car, even for a few minutes.