Thousands of people have suffered pollen allergy asthma attacks in the state of Victoria and hospitals are stretched to their limits, with thousands of residents phoning to report breathing problems.
The Herald Sun reports that 8,500 people were treated in hospitals for asthma in 24 hours.
In a statement on Sunday, Australia's health department said: "There have now been six deaths that may have occurred as a result of conditions relating to the thunderstorm asthma events on Monday."
Included in the six people who died are father-of-two Clarence Leo, 35-year-old Apollo Papadopoulos, 20-year-old law student Hope Carnevali and student Omar Moujalled.
Thunderstorm asthma is only known to have occurred several times before in Australia.
According to the Met Office, the rare outbreak is not yet fully understood as it is caused by a combination of factors. It is triggered during the summer by a combination of large storms caused by converging masses of air, high humidity and possibly high levels of air pollution.
As large thunderstorms pass over the land, they draw up pollen and spores, with very high humidity in the cloud causing these to break into pieces and penetrate deep into the lungs.
The Guardian reports that Melbourne has suffered the most lethal episode of thunderstorm asthma on record.
Professor Anthony Seaton, from the University of Aberdeen, told the newspaper: "I don't know of any event as severe as this."
Thunderstorm asthma attacks have previously been recorded in the UK, Italy and America.
In June 1994, a large outbreak of thunderstorm asthma in London led to 640 patients overwhelming hospital emergency departments.
Experts have warned that climate change is likely to bring an increase in frequency of the deadly storms.
Weird weather and strange phenomena around the world
Weird weather and strange phenomena around the world
Tornados have been ripping through parts of the USA at an alarming rate during 2011. This example was captured on camera in Limestone County, Alabama, in April. A tornado is a violent, rotating column of air that it is contact with a cumulonimbus cloud and the ground. Also called twisters, they’re characterised by the condensation funnel that touches the earth, and are surrounded by clouds of dust or debris.
On 11 January, 2010, two pranksters decided to drive their car along the frozen Union Canal in Winchburgh, West Lothian, Scotland. Unfortunately for them, the thaw had already started to set in. The canal froze solid during he longest spell of freezing weather in the UK for almost 30 years.
This dust storm engulfed the desert city of Bikaner, in the western Indian state of Rajasthan on 2 April, 2010. The town was already broiling in temperatures of 39C. Dust storms happen when strong wind carries loose sand and dust away from one area and deposits it in another.
This image of the Northern lights was captured in the Takotna, Alaska checkpoint during the Iditarod Trail Sled Dog Race in March 2011. Occurring just within the Arctic and Antarctic circles, the Northern lights – or Aurora borealis, to give them their Latin name – are the light display in the sky caused by the collision of charged particles directed by the Earth's magnetic field.
This impressive rainbow resulted from a spectacular storm and was photographed in Brandon Hill Park near Clifton, Bristol, in the UK on 27 August, 2010. The rainbow seems to rise from the top of Cabot Tower - which is itself 105ft tall - showing its immense scale. Rainbows are an optical phenomenon that occur when the sun shines on to moisture droplets in the atmosphere.
This set of footprints in freezing rain was snapped in Lexington, Kentucky, USA on 16 December, 2010. Rain that falls and becomes ‘supercooled’ when surface temperatures are below freezing point can freeze on impact with anything it touches, unlike snow which remains only partially frozen. The resulting ice is known as glaze. Freezing rain is one of the deadliest weather conditions, bringing down power line and causing numerous road traffic accidents and personal injury.
This example of smog was pictured hanging over Moscow, on 7 August, 2010, and was caused by the billowing smoke from peat bog and forest fires. Smog was originally a description of the pollution resulting from factory smoke and fog in the 1900s. Today it’s more often caused when sunlight reacts with car exhaust, coal power plants or factory emissions and the compounds released from petrol, paints and solvents.
This crashing wave was caused by the approaching of the Hurricane Earl in Fajardo, Puerto Rico, in August, 2010. Earl battered some islands across the northeastern Caribbean with heavy rain and roof-ripping winds, rapidly intensifying into a major storm on a path projected to menace the United States. Hurricanes are triggered by low pressure areas forming over warm ocean waters.
In March 2011, the 'supermoon' was the closest it had been to earth for18 years lighting up the night sky from just 221,567 miles (356,577 kilometers) away. This snap was taken from Huntington Beach in Los Angeles.
Rainstorms come and go, but not usually as dramatically as this downpour which completely flooded the town of Wuzhou in southwest China on 9 June, 2010, proving that the trusty umbrella isn’t always protection enough...
Ash covered everything for thousands of miles after the eruption of Iceland's Grimsvotn volcano in May 2011 sent clouds of ash high into the air, carrying it toward the European continent on the wind, disrupting flights for the second time in less than a year.
This magnificent lightning strike hit a tower during a thunderstorm in Zurich, Switzerland on 12 August, 2010. Lightning occurs when the balance between the negative charge of storm clouds and the positive charge of the earth is redressed by a current passing between the two - with literally stunning results.
This halo around the sun was photographed on the island of Spitsbergen in the Arctic Circle on 19 April, 2011. These halos - spectacular and eerie at the same time - are caused by ice crystals in high clouds. They tend to occur during the summer months, during ‘midnight sun’ season in the Arctic and Antarctic Circles.