Residents are warned heavy rain could bring flash flooding, large hailstorms and dangerous driving conditions, Bureau of Meteorology senior forecaster Miriam Bradbury said on Sunday.
"We are going to see a severe storm potential through Sunday afternoon and evening across the central parts of Victoria, including much of the greater Melbourne area, pushing up across much of the Riverina of NSW as well," she said.
The Victorian chief health officer warned there was an increased chance of epidemic thunderstorm asthma across the state's northern country region.
Epidemic thunderstorm asthma is where a large number of people suddenly develop asthma symptoms over a short period and is thought to be triggered by a combination of high pollen levels and a certain type of thunderstorm.
In November 2016, Melbourne experienced the world's largest epidemic thunderstorm asthma event, overwhelming emergency services and leading to 10 deaths.
Among those affected were people with seasonal hay fever who had never had asthma.
Asthma sufferers are urged to carry their reliever puffers with them at all times.
In Queensland, the severe storm risk extends across much of the southeast, including the southeast coast, much of the Darling Downs and the Wide Bay and Burnett area.
Ms Bradbury warned the Brisbane area, the Sunshine Coast and the Gold Coast were also in for a torrid time.
"Through this afternoon and evening, we may see some very dangerous thunderstorms developing in these areas," she said.
"It's a good idea to be keeping a close eye out for any warnings we do need to issue."
Damp conditions are expected to linger along much of eastern Queensland next week as a low-pressure trough continues to draw in moisture against the coast.
Tuesday is likely to be the wettest day.
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