A ninth person has died of thunderstorm asthma after a freak weather event late last year.

About 8,500 people sought hospital treatment when the weather changed abruptly on November 21, as a cool change and thunderstorms swept across Melbourne.

Eight people died in just over a week following the event, with the department saying at the time one person remained in critical condition in intensive care.

Today a release from the Victorian Department of Health and Human Services confirmed another person had died.

It added that no more patients remained in hospital and, with the pollen season in Victoria now over, it is not expecting thunderstorm activity to trigger any more instances.

The Victorian Government announced a review into the public health system's response to the cases, while an inquest by the coroner was also flagged in December.

Incidents of thunderstorm asthma are sparked by large storms, like a cool change in spring, that can cause significant breathing problems to people who do not have the condition.