One year after “thunderstorm asthma” sent 8,000 Australians to local hospitals, health officials are warning of more weather-related exacerbations this month.

Locals in an Australian state hit by a thunderstorm asthma outbreak last year have been warned of a “moderate” health risk this week.

Nine people died in Melbourne last November after rain and wind triggered asthma attacks brought on by pollen.

On Sunday, authorities asked people in Victoria to plan for asthma conditions, although they may not eventuate. It is the first warning since an alert system was introduced following a review into last year’s event.

There are three tiers in the classification system – low, moderate and high.

More than 8,000 people were treated in hospital during last year’s outbreak. The strain on health resources was akin to a disaster event such as a major bushfire, authorities said.