Asthma is no fun at the best of times. On this occasion though, a rare storm triggered breathing problems for hordes of people in an Australian city.

The unusual phenomenon called "thunderstorm asthma" resulted in a total of five deaths, with over 30 people initially rushed to intensive care and 1900 emergency calls between 6 p.m. to 11 p.m. Monday night.

"We essentially had a day's workload within five hours. This includes 200 cases for asthma, and we were seeing asthma in people who had not experienced breathing issues before," Ambulance Victoria's Executive Director of Emergency Operations, Mick Stephenson, said in a emailed statement.

The Agereported 20-year-old Hope Carnevali died while waiting for an ambulance, which arrived 31 minutes after the call. The second death was 18-year-old Omar Moujalled, who had finished his last high school exam only a few days before. Apollo Papadopoulos, 35, and father-of-two, Clarence Leo have also since died from asthma-related complications according to news.com.au.

A statement via email from Victoria's Department of Health and Human Services confirmed the latest victim, who's yet to be identified, has died Saturday Nov. 26. while six people remain in intensive care.

What the hell is thunderstorm asthma?

Thunderstorm asthma can affect regular sufferers of the disease, or non-sufferers who get hay fever. Symptoms include wheezing, difficulty breathing, tightness of the chest and coughing.

Robin Ould, CEO Asthma Foundation of Victoria, told Mashablethere were extremely high levels of grass pollen in the air on Monday.

"There were over 100 pollen grains per cubic metre in the 24 hours building up to that event," Ould said.

"When you have that much pollen, and it's followed up by a storm, the pollen grains get wet. They break up, and the small particles -- which are allergens -- become dispersed quite widely by the wind."

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The job of the small hairs in the nose is to stop pollen from getting into one's respiratory system. But as the pollen is broken down into smaller bits by wet weather, they easily can get past the hairs.

"Because those pollen grains are so small, they can get into the lungs rather than being just trapped in the nose," he said.

"Once the allergens are in the lungs they can trigger an asthma attack for those people whose trigger is pollen, or people who have hay fever but don't necessarily have asthma.

"Because pollen gets into the lungs, they do become susceptible to having asthma symptoms, or an asthma attack."

'It's really a rare event'

The last time a thunderstorm asthma event happened in Melbourne was on Nov 25. in 2010, and before that it was in 1995 in the Wagga Wagga area of the state of New South Wales.

Incidents have also been recorded in London and Birmingham in the UK, as well as Naples in Italy.

Ould stresses that it's hard to know when such an event will happen, and that asthma sufferers -- who are 1 in 10 Australians -- should know how to manage their symptoms.

"It's really a rare event and difficult to predict ... our message is that you should have a management plan and a good relationship with your doctor. If you're a prevention program, you should stick to it and adhere to it," he said.

Make sure you carry that Ventolin around if you need it, folks.

UPDATE: Nov. 27, 2016, 1 p.m. AEDT Fifth death announced by Victoria Department of Health and Human Services.