Sixth death after thunderstorm asthma in Melbourne

Thunderstorm asthma happens when a thunderstorm, sudden change in humidity, a northerly wind change and high pollen count are combined.

A sixth person has died almost a week after Melbourne was hit by an unprecedented thunderstorm asthma outbreak.

The patient, who'd been in a critical condition, died in an Eastern Health hospital on Saturday night as a result of thunderstorm asthma causing other "medical complications", a hospital spokeswoman said.

"There have now been six deaths that may have occurred as a result of conditions relating to the thunderstorm asthma events on Monday," the health department said in a statement on Sunday.

Five patients remain in intensive care in Melbourne hospitals. Three are in a critical condition.

A further 12 are in hospital battling a variety of respiratory and related conditions.

The news of the sixth death came as Premier Daniel Andrews and Health Minister Jill Hennessy announced a $500 million funding boost for the state's ambulance services.

The package - which the government says is in addition to $144 million provided in the 2016/17 budget - will result in 450 new paramedics being employed over three years.

Labor also plans to establish six new "super response centres" across Melbourne to meet a growing demand driven by population growth.

"We know that in an emergency every second counts," Hennessy said in a statement on Sunday.

"That's why we're giving our paramedics the new resources they need, where they are needed most."

Monday's asthma storm overwhelmed emergency services and hospitals.

Paramedics dealt with an unprecedented 1900 emergency calls in five hours on Monday evening as the phenomenon swept the state.

At one point there were 140 code one cases occurring at the same time.

Melbourne hospitals across Monday and Tuesday treated more than 8500 patients.

- AAP