Rohan Smith of news.au.com reports doors swung wide open at homes around Melbourne on Monday afternoon in hopes a looming thunderstorm would bring with it a cool change.

It did, but it carried with it something else. The combination of warm weather, a high pollen count and stormy conditions produced what experts call “thunderstorm asthma,” an extremely rare and dangerous phenomenon that saw Victoria run out of ambulances for an entire hour.

Fairfax reported on Tuesday that two people are believed to have died while waiting for ambulances on Monday.

Those who suffered were not prepared. Most said they hadn’t experienced asthma since childhood. They all had one thing in common: Hay fever.

“I’ve never had asthma but do get hay fever, mainly itchy eyes and sneezes, but there were weirdly no other hay fever symptoms (on Monday),” Kate Craig, from Melbourne’s inner west, told news.com.au.

“It hit me all of a sudden about 7.30 last night, I felt like I couldn’t take a full breath and had an awful, chesty, hacking cough. I thought I must have just inhaled some spices while cooking — that’s what it felt like.”

Gary Nunn said he was in transit when he began to have trouble breathing.

“I’d had bad hay fever all day in Melbourne. In the early evening I got to Melbourne Airport and noticed a new symptom: I was struggling to breathe. This had never happened before,” he said.