One of the two people who died as a result of an "unprecedented" outbreak of thunderstorm asthma has been remembered by family as a "kind-hearted" woman.

Hope Carnevali died last night, after suffering a horrific asthma attack.

The 20-year-old lay on her lawn for more than 30 minutes waiting for an ambulance to arrive, while her family desperately performed CPR.

"My brother tried CPR for 20 minutes, he just kept going, there was nothing he could have done," Ms Carnevali's uncle John told 9NEWS.

"She was a kind-hearted, beautiful, gorgeous little girl," he said.

The roof was ripped off a carport in Altona Meadows. (Amanda Kemp/Supplied)

Ambulance Victoria's Mick Stephenson said paramedics dealt with a six-fold increase in calls last night, as a wild storm moved through Melbourne.

One patient who rushed himself to St Vincent’s Hospital suffering breathing difficulties said he "thought he was dying".

Guo Lu told 9NEWS he was struggling to breathe and feeling "worse and worse" from coughing and wheezing.

"I came here to emergency, the nurse checked me very fast," he said.

"I felt like I was dying. They [medical staff] saved my life."

Almost 2000 triple zero calls for ambulances were made when the weather turned from around 6pm to 11pm. Ambulance Victoria said usual levels would only see them take around 345 calls for help.

Ambulance Victoria’s Executive Director Emergency Operations Mick Stephenson said most calls were for patients in the west of Melbourne.

A surge of wild weather passed through Victoria last night. (Amanda Kemp/Supplied)

"We essentially had a day’s workload within five hours," Mr Stephenson said.

"In the 15 minutes from 7pm when we would expect about 30 triple zero calls for ambulance there were 200 calls – that’s a call every 4.5 seconds."

Every available ambulance had to be dispatched during the height of the storm, with 50 extra vehicles needed and Metropolitan Fire Brigade members deployed to assist.

“We had an extraordinary influx, about an additional 100 patients who all arrived within a matter of hours. We had so many that a code brown team had to be set up, and we even considered setting up a second emergency department within the foyer of the hospital,” St Vincent’s Hospital Media and Communications Manager Kathy Bowlen said.

Ambulance Victoria State Health Commander Paul Holman said in his 40 years, he had never seen anything like it.

"I think a spike in calls would be the understatement of a century," he said.

Paramedics called in help from the Metropolitan Fire Brigade, police and doctors to help with the demand after they ran out of ambulances. At one stage, 190 people required help.

"These were quite sick patients," Mr Holman said, saying most jobs were code ones or top priority emergencies.

On a normal night, there would be about 10-20 cases waiting mostly of low or middle priority level.

The State Emergency Service received more than 350 calls for help for damaged homes and trees down, despite the mercury tipping 35 degrees in the city yesterday.