Australia on alert as heat tops 40C

Severe fire warnings as strong winds push risk even higher. Photo / Supplied

Australia continues to swelter as heatwaves push temperatures into the 40s across a continent that has become a tinderbox.

Firefighters were battling dozens of outbreaks yesterday - none so far threatening life or property - and authorities were warning of health risks as ambulance services treated people struck down by the heat.

In Melbourne, officials renewed warnings against leaving children in cars after they were called to a number of cases by passersby. Although most had been left only briefly, Ambulance Victoria said temperatures inside a car could soar by up to 20C within minutes.

Surf lifesavers have also urged caution, with hundreds of people pulled from dangerous seas around the country.

Extreme temperatures have been driven north through South Australia and Victoria by weather patterns radiating out from the interior.

In Queensland, hot northerlies are being funnelled between a high-pressure system to the east and a low in the centre, pushing temperatures into the 40s across the southwest of the state in a heatwave that is expected to keep the heat well into the 40s for the rest of the week.

Strong, hot winds and soaring temperatures are raising the already dangerously high risk of grass and bush fires, fuelled by the lush growth that followed the end of the drought.

Prime Minister Julia Gillard yesterday urged extreme caution and said people should listen to and obey advice from emergency services.

Total fire bans are in place across large areas of South Australia and Victoria, and electricity authorities cut power to thousands of homes in SA to reduce the risk of powerlines sparking deadly fires.

Yesterday, severe fire weather warnings were issued in SA's northern pastoral areas and in the Flinders and Riverland regions as temperatures again moved into the 40s, northerly winds averaged up to 35km/h and relative humidity dived below 10 per cent.

The state's Country Fire Service said fires burning under these conditions were likely to be fast-moving and uncontrollable.

In Victoria, the Bureau of Meteorology issued similar warnings for the northern country region: temperatures in the 40s, low relative humidity and winds averaging 40km/h. The danger has been increased by forecasts of thunderstorms and dry lightning.

Western Australia issued severe fire danger warnings for 13 central west shires, including the coastal city of Geraldton north of Perth.

Across the continent, above-average rainfall over the past year increased soil moisture, encouraging vigorous growth that is now rapidly dehydrating and creating the highest grass-fire threat for decades. Driven by hot, strong winds, grass fires can race across open country at more than 20km/h, change direction quickly and without warning, and trap entire communities or traffic on roads.

Such winds can also pull fire into the upper atmosphere, dropping burning embers kilometres ahead of fire fronts.

In the past three days firefighters have battled dozens of grass and bush fires in SA, Victoria, New South Wales, Queensland and WA.

NSW emergency teams were yesterday trying to contain a fire burning out of control in rugged country in the Guy Fawkes River National Park, near Armidale in the New England Tablelands.

In WA, units were battling bushfires near the Perth suburb of Wanneroo, the Goldfields city of Kalgoorlie, and others in the north and south of the state.