A thunderstorm asthma warning has been issued for most of Victoria, with hundreds of people already in hospital.
The warning, which was expected to remain in place until early Thursday, covered the entire state apart from areas west of Ballarat and north of Kerang.
“We are seeing an increase in people suffering asthma symptom across parts of Victoria,” the VicEmergency warning said.
“People may experience asthma symptoms or difficulty breathing due to the combination of thunderstorm activity and high grass pollen levels.”
There were more than 230 people admitted to hospital with asthma symptoms in the past 24 hours, a considerable increase on normal figures.
Three of the five districts subject to the warning are expected to return to a low risk of asthma on Thursday.
The warning system was developed after Melbourne experienced the world’s worst recorded thunderstorm asthma event in November 2016.
The event, caused by a combination of high pollen, strong winds, high temperatures and air moisture before a cold front, sparked an unprecedented surge of emergency calls across Victoria. Ten people died and about 14,000 were taken to hospital.
The thunderstorm asthma monitoring season typically runs from October to December. There have already been multiple warnings issued this season.
- Australian Associated Press contributed to this report