A cold snap will hit Australia’s south-east over the weekend, with cool winds and rain sweeping up through Tasmania to Brisbane from Friday evening.
Victoria will face chilly weather, showers and potential thunderstorms on Saturday, with Melbourne expecting up to 10mm of rain and potential hail amid daytime temperatures of just 12C.
Showers and brisk winds are forecast for eastern New South Wales by Saturday and into Queensland by Sunday, according to the Bureau of Meteorology.
Runners in the Sydney marathon on Sunday will grapple with winds and showers moving inland from the coast over the day, before rain clears on Monday.
The cold airmass had already hit Tasmania on Friday afternoon and was forecast to overnight bring showery, windy weather and snow at altitudes as low as 200m, according to Weatherzone meteorologist Angus Konta.
Hobart is forecast to be pelted with up to 7mm of rain and small hailstones, delivered by below-average temperatures of 11C or lower, according Konta.
A warm, windy weekend is forecast for central and western Australia, with gusty winds increasing the risk of fire, while occasional showers are expected in Darwin and northern Queensland.
Australians in many eastern areas face an increased risk of severe storms and flash flooding from now until January, with some communities also at risk from extreme heat and bushfires, according to the government.
The bureau said climate models and long-term forecasts pointed to several increased risks during the “high-risk weather season” from September to January.
The season for thunderstorm asthma events – which usually runs between October and December – could start early, with an above-average risk for the ACT and surrounding areas.
The bureau, alongside the National Emergency Management Agency (Nema), have provided briefings to MPs, business and industry sectors and state authorities and was planning to “war game” disasters at a two-day national disaster preparedness summit next week.
Matt Collopy, manager of environmental prediction at the bureau, told a briefing on Friday that climate modelling was showing a chance of above average rainfall for much of the east of the country over the coming three months.
This, alongside many areas where soil moisture was high, would increase flood risk. Tasmania particularly had increased risk of riverine flooding between now and January, the briefing said.
Collopy said: “For the eastern parts of Australia where you have increased chance of rainfall and you have existing runoff and soil moisture levels, then we are looking at increased potential flood risk and that’s something we are watching very closely with our emergency services partners.”
Higher soil moisture and increased rainfall chance did suggest there would be fewer dust storms than usual, he said.
Warmer than average ocean temperatures and the rainfall outlook were also raising the risk of severe storms and east-coast lows, with south-east Queensland and northern NSW particularly at risk.
The bureau releases a detailed outlook in October on numbers of tropical cyclones expected, but at this stage the outlook was for “near-average risk”.
Collopy said the average number of cyclones forming each season in the Australian region was about nine, a slight fall in recent decades, “but these systems we are seeing have been stronger”.
“We may see less cyclones, but the intensity of these systems has increased.”
Last week fire authorities warned of an early start to the bushfire season for parts of Victoria and south-east SA this spring, with large areas of Queensland and the Northern Territory also facing an increased risk of bushfires.
An outlook for summer is expected to be released in late November.
Joe Buffone, deputy coordinator-general at Nema, said there had been a “significant shift” in aircraft capability to respond to disasters, including bushfires.
The government now has six emergency camps that can be deployed to disaster areas, and provide temporary shelter, power and sewage facilities for up to 700 community members or 1,400 workers.
